Magnetism in Gemstones
An Effective Tool and Method for Gem Identification
December 2015
A photo of a pink Malaya Garnet that fluoresces pink under long wave UV light due to chromium was added to the Malaya Garnet section on page 3 of Garnets.
Information and photos of a pink Pastel Pyrope Garnet that fluoresces red under long wave UV light due to chromium was added to the Pastel Pyrope section on page 4 of Garnets.
Photos and a new section titled Lecuo Garnet were added to page 5 of Garnets. These Leuco Garnets fluoresce pink under long wave UV light due to chromium. In the same section, a photo with information about a bi-colorLeuco Garnet (green & colorless) was added.
November 2015
A new photo of a yellow Tourmaline pear from Tanzania was added to the section on Yellow Tourmaline on page 2 of Tourmalines.
A new photo of a blue Garnet cushion from Tanzania was added to the Color Change Garnet section on page 2 of Garnets.
A photo of Rosolite Garnet rough from Mexico was added to the Grossular Garnet section on page 5 of Garnets.
A new photo of blue Spinel round with significant cobalt content was added to the section on Blue Spinel on page 1 of Spinel.
Three new gems were added to the Magnetic Susceptibility Index: Anglesite (inert), blue Kornerupine (weak), and Orpiment (inert).
October 2015
A new photo of Amethyst as added to the section titled Aluminum at the bottom of page 4 of Overview.
A photo of red Hydrogrossular Garnet was added to the Hydrogrossular section on page 5 of Garnet, and on the same page a photo of a yellow round Mali Garnet was added to the Mali section.
Under the Blue Sapphire section on the Sapphire & Ruby page, it is suggested that the iron in Fe2+-Ti4+ charge transfer may not be magnetically detectable because the concentration of iron is simply too low rather than to any mechanism of chemistry or physics.
September 2015
Several photos were added last month. On page 4 of How to Use a Magnet, in the box titled Testing Mineral Specimens, a photo of a mineral being tested by the Floataion Method was added. On the same page, a photo of Rhodolite Garnet being picked up by a magnet was added to the section titled Separating Look-alike Gems. Continuing on the same page, a photo of synthetic blue Forsterite as an imitation of Tanzanite was added under the section titled Synthetic and Imitation Gems. Synthetic Forsterite was also added to the Magnetic Susceptibility Index.
Two photos of rare Opals that fluoresce green due to Uranium were added to the section titled Uranium on page 4 of Overview.
A Top Menu for the website pages was added to the top of all pages. Previously, it could only be seen on the Home page.
August 2015
A photo of Demantoid Garnet being picked up by a magnet was added to the Pick-Up Responses section on page 2 of How To Use a Magnet for Gem Identification.
A photo of blue Quartz magnetic due to blue tourmaline inclusions was added to the Magnetic Inclusions section on page 3 of Overview of Magnetism in Gemstones.
Information and a photo of a green Quartz doublet was added to the Faceted Doublets section on the page titled 10 Practical Uses for Gem Identification.
July 2015
Information and photos of green Spinel, Mahenge Spinel and blue flux-grown synthetic Spinel were added to page 2 of Spinel.
A photo of an ultra-compact carrying case for a magnetic wand was added to page 1 of How To Use a Magnet.
A photo of metal jewelry that picks up with a magnet was added to the Gems in Jewelry section on page 4 of How To Use a Magnet. On the same page under Magnetic Inclusions, a photo of blue Peruvian Opal with black chromite inclusions was added.
Photos of the purest Pyrope Garnet and the palest Pyrope we have tested, pink Pastel Pyropes from Madagascar and Tanzania, were added to page 4 of Garnet. The purest Pyrope is 87% Pyrope.
A new section titled How Sensitive is Our Magnetic Wand was added to page 1 of Overview of Magnetism. Estimates for detectable concentrations of various metals in gems are given. On the same page, the coloring agent Uranium was separated from the list of rare earth elements, as Uranium is not a rare earth element.
June 2015
Photos of opaque black Obsidian, transparent black Obsidian and banded Onyx were added to the section on Black Gems on page 3 of How to Use a Magnet for Gem Identification.
New photos of natural and synthetic Ruby were added to the Ruby section of the Sapphire and Ruby page.
A new photo of yellow synthetic HPHT Diamond with metallic inclusions was added to the Diamond page.
A new 2-page section about magnetism in Spinel was added to the website. Information about all colors of Spinel, including synthetic Spinel, is included in this in-depth look at gem Spinels. Seven new references specifically about Spinel were also added to the bottom of the Resources & Links page.
May 2015
A new paragraph was added below the Periodic Table of Elements on page 1 of Overview of Magnetism. This paragraph presents some estimated levels of concentration of metals that can be detected with a magnetic wand. Just below this paragraph, a photo of a S.Q.U.I.D. magnetometer was added to the gay box titled Micro-Magnetism of Inclusions.
On page 4 of Overview of Magnetism, the section titled Rare Earth Metals was expanded to include information on cerium and uranium as coloring agents. A photo of a rare green metamict Zircon that is magnetic due to uranium was added to this section.
A photo of a synthetic Star Ruby was added to the bottom of the page titled Sapphire and Ruby.
The Magnetic Susceptibility Index was updated to include strongly magnetic Dunilite (under Peridot), man-made magnetic pink Glass colored by the rare earth metals, and an expanded section on Spinel is presented on the Index.
A new study of magnetism in Spinel is being undertaken, and a new page titled Spinel will soon be added.
April 2015
A list of the 4 rare earth metals that cause magnetism and color in natural gemstones was added to page 1 of Overview of Magnetism in Gemstones.
A spectrometer graph of blue Spinel was added to page 5 of Overview of Magnetism in Gemstones. illustrating how iron (Fe3+) in natural blue Spinel causes magnetic attraction, while the absence of iron in synthetic blue Spinel results in diamagnetism.
A spectrometer graph of blue Sapphire was added to the Sapphire and Ruby page. The graph illustrates how iron (Fe3+) content in natural Sapphire causes magnetism, in contrast to the absence of Fe3+ in diamagnetic synthetic Sapphire.
Two spectrometer graphs of blue Tourmaline were added to page 1 of Tourmaline. The first graph shows the presence of cryptic iron (Fe3+) in a bicolor Indicolite. The second graph illustrates how progressively stronger magnetic responses correspond to progressively higher concentrations of iron (Fe2+).
A spectrometer graph along with a paragraph of information about blue Color Change Garnet was added to the Color Change Garnet section at the bottom of page 2 of Garnet. The graph illustrates how the presence of chromium/vanadium in addition to manganese creates blue and red colors in blue Color Change Garnet.
A proposal that Andradite Garnet is an allochromatic species is presented in the first paragraph about Andradite on page 5 of Garnet.
A spectrometer graph of colorless Mali Garnet was added to the Mali Garnet section on the same page. The graph illustrates the presence of colorless or cryptic iron (Fe3+) in Mali Garnet.
March 2015
A new photo of Peridot was added to the Home page. Also, an information gray-box about Peridot as a partially allochromatic and partially idiochromatic gem was added to page 3 of Overview of Magnetism in Gemstones.
A new photo of natural vs synthetic blue Spinel, and a photo of natural orangey pink Spinel, were added to page 4 of How to Use a Magnet for Gem identification.
A broken link to gemologytools.com for purchasing magnetic wands was fixed on page 1 of How to Use a Magnet for Gem Identification.
February 2015
Information and a photo about using a spectrometer to detect magnetic metals in gems was added to the section titled Spectroscopy in Relation to Magnetism on page 5 of Overview of Magnetism in Gemstones.
Magnetic information and photos of Uvite Tourmaline as added to the Brown and Orange section on page 1 of Tourmalines.
Magnetic information and a photo of Rossmanite Tourmaline as added to the Purple section on page 2 of Tourmalines.
Paraiba Tourmalines that are primarily red in color can exist if there is sufficient copper to create purple undertones. The section labeled Pink and Red on page 3 of Tourmalines was modified to indicate this.
The existence of rare cat’s eye Garnets was noted under the Pyrope section of page 2 of Garnets.
Information and photos of red Pastel Pyropes was added to the Pastel Pyrope section on page 4 of Garnets.
A photo of red Andradite Garnet was added to page 5 of Garnets. On the same page, information and a photo of colorless Andradite was added. Further down on the same page, a photo of yellow Hessonite was added.
The Magnetic Susceptibility Index was updated to include 15 new gems:
Rossmanite Tourmaline (translucent)- Weak
Red Uvite Tourmaline- Strong
Green Uvite Tourmaline- Inert
Pyroxymangite (translucent)- Picks Up
Chrome Kyanite (blue-green) - Inert to Weak
Chrome Enstatite- Strong
Bustamite (translucent)- Picks Up
Brazilianite- Inert
Herderite- Inert
Sapphirine- Weak to Moderate
Shattuckite- Strong
Viridine (Mangan- Andalusite)- Moderate
Ekanite- Weak
Parisite- Drags
Magnesite (transparent gray)- Drags
January 2015
A new photo of a glass imitation Peridot gem, as well as photos of a weakly
magnetic blue Glass gem and Goldstone Glass were added to the section titled
Synthetic and Imitation Gems on page 4 of How to Use a Magnet for Gem
Identification.
A photo of a strongly magnetic purple Tourmaline was added to
page 2 of Tourmalines.
On page 5 of Garnets, Russia was added as another
geographic origin for Mali Garnet.
December 2014
The Magnetic Susceptibility Index was updated to show Axinite as 3 separate species- Ferroaxinite, Manganaxinite and Magnesioaxinite- with 3 different ranges of magnetic susceptibility. Only colorless Magnesioaxinite (Weak) does not show a drag response. Also added to the Index are transparent Sugilite (strong), transparent Dolomite (inert). Under Spinel, the zinc Spinel species Ghanite (strong) was also added.
Under the Rhodochrosite and Rhodonite section on page 3 of How To Use a Magnet for Gem Identification, a photo of transparent red Rhodchrosite from South Africa was added. This gem has an appearance similar to red Garnet. On the same page under Hematite, photos of “Iron Rose” Hematite and “Strawberry Quartz” with Hematite inclusions were added.
Under the Spinel section on page 4 of How to Use a Magnet for Gem Identification, a photo of natural red Spinel was added next to the photo of synthetic red Spinel. On the same page under the Country of Origin section, Madagascar was added as another country where diamagnetic Fire Opal can be found.
November 2014
A number of broken links in the website were repaired. The broken links pointed to Gems & Gemology references, and to pages in the Overview section.
Two photos of green Mali Garnets were added to the Mali Garnet section on page 5 of Garnets.
A new page titled Sapphire and Ruby was added to the website. This page presents results of a study of magnetism involving approximately 50 Sapphires and 50 Rubies. Information about Sapphire and Ruby that had appeared in other pages of the website was removed and consolidated onto this one page.
October 2014
The Overview section now has 5 pages. Page 2 of Overview of Magnetism in Gemstones was separated into 2 pages- page 2Diamagnetic Gems and page 3Factors that Affect Magnetism in Gemstones.
New information on heat treatment of Sapphire as related to magnetism was added to the section titled Valence State on page 3 of Overview of Magnetism. New photos of heated and unheated Sapphire were added.
A new photo of brown Apatite was added to the section on Rare-earth Metals on page 4 of Overview of Magnetism in Gemstones.
More information about separating natural Sapphire from synthetic Sapphire was added to the section titled Synthetic and Imitation Gems on page 4 of How to Use a magnet for Gem Identification. Photos of natural & synthetic Padparadscha Sapphire were also added.
On the same page, information about Sapphire was added to the section titled Country of Origin. Information is provided about low-iron and high-iron Sapphires from different localities and how this affects magnetism. New Sapphire photos are included in this section, including a photo of a genuine Sapphire from Kashmir, India. In the same section on Country of Origin, photos of Mexican and Brazilian Fire Opal were added.
On the Magnetic Susceptibility Index, the section on Sapphire under Corundum was updated.
September 2014
A new photo of a Uvarovite Garnet specimen from Russia with larger-than-usual crystals was added to the Uvarovite section at the bottom of page 5 of Garnets. A paragraph was also added to the bottom of this page presenting information about Uvarovite from Deer, Howie and Zussman's 1982 book Orthosilicates, including evidence that Chromium Grossular Garnets exist as intermediaries between Uvarovite and Grossular.
The section title Blog on our website menu was changed to Comments to better reflect the nature of the entries added by readers.
August 2014
A reference to the Garnet Group by Deer, Howie and Zussman was added to the Garnet Section on the References & Links page. Though technical, this 1982 book edition is the most comprehensive examination of Garnet chemistry and geology that has ever been published.
June 2014
A section titled Other Resources was added to the Resources and Links page. This section contains links to 9 resources cited at various points throughout the body of this website. A section titled Tourmaline References was also added. It contains 7 references cited throughout the Tourmaline pages.
The following sentence about cryptic ions was added to page 2 of Tourmalines: “Cryptic ions do not absorb enough light to be visible as absorption bands under a spectroscope, but they can be detected with a spectrometer.”
A photo of naturally glittering Specular Hematite was added to the Hematite section at the bottom of page 3 of How to Use a magnet of Gem Identification.
The following sentence about floatation of large mineral specimens was added in a gray box under the section titled Rough Stones near the top of page 4 of How to Use a magnet of Gem Identification: “Large mineral specimens of any type can be tested for magnetic response via the floatation method by placing them inside a large plastic tub or lid floating in water. Mineral specimens of Garnet crystals attached to host rock or matrix are generally too heavy to show a pick-up response, but most specimens (other than Grossular Garnet rough) will show a strong magnetic response when floated.”
May 2014
Two gems were added to the Magnetic Susceptibility Index: Translucent Serpentine (Weak) and Taafeite (Strong). An SI value of 998 for UvaroviteGarnet was also added to the Index. The response and SI value for synthetic Ruby was changed from Inert-Strong, SI 0-195 to Inert-Weak, SI 0-17.
A new study of magnetism in Ruby revealed some new information, including how Ruby fluorescence is related to magnetism. This information was added to section #5 on the page titled 10 Practical Uses for Gem Identification.
The following sentence about Ruby was added to the section about Chromium on page 3 of Overview of Magnetism in Gemstones: “Ruby, particularly synthetic Ruby, is one of the few gems that contains enough chromium to be detected with a magnet, and concentrations are barely detectable in this gem.” At the bottom of the section about Chromium, photos of Chrome Chalcedony and Chrome Garnet were added.
A rare example of a large 3mm Uvarovite crystal from Afghanistan was tested for magnetic susceptibility and composition. Until now, no data about composition of this species had been obtained. New information and a photo of this Garnet species was added at the top of page 5 of Garnets. Uvarovite was also added to the bar graph on page 3 showing relative magnetism in Garnets.
Regarding heat treatment of Demantoid Garnet, the following sentence was added to page 5 of Garnets: “Fe3+ is more magnetic than Fe2+, we can predict that the magnetic susceptibility of Demantoid Garnets will be a bit lower after heating, and that composition data based on SI and RI readings of heated gems may be compromised. Actual experiments measuring the susceptibility of Demantoids before and after heating are needed to prove this theory.”
April 2014
The page about Paraiba Tourmalines was re-written, and it can once again be viewed as page 3 of Tourmalines. Revisions in the text and photos on this page reflect a smaller sample size, where all gem samples have been confirmed as copper-bearing through analysis with a spectrometer.
Under the Grossular Garnet section on page 5 of Garnets, it was noted that vanadium can be a coloring agent for some green Grossulars in addition to, or instead of, chromium. Vanadium is not detectable with a Chelsea filter.
March 2014
Page 3 of the Tourmaline section titled Paraiba Tourmalines has been omitted. After using a UV-Vis-NIR spectrometer to test the Paraiba Tourmalines discussed on this page, it was found that a number of samples were not true Paraiba Tourmalines colored by copper. Page 3 will be re-instated once further testing is completed and results are rewritten. Information about blue Paraiba Tourmalines is now presented on page 1 of Tourmalines under the section titled Blue.
February 2014
Sanidine, a type of Feldspar that has similar chemical composition as Orthoclase (actually it is a polymorph of Orthoclase) was tested and added to the Magnetic Susceptibility Index. The gem showed a Moderate magnetic response, but the gem was too large for a quantitative measurement to be taken with the magnetic susceptibility balance. There is nothing else to report for February.
January 2014
The Dropdown Menu across the top of the Home Page was fixed so that there no longer any problems with clicking on the page links.
A highlighted box explaining Cryptic Ions was added to the page titled The Magnetic Meals that Color Gems. On the same page in in the box titled One Metal, Multiple Colors?, “geometry of the crystal lattice sites” was corrected to say “geometry of the molecules containing metal ions”.
Three more gems were added to the Magnetic Susceptibility Index: Johachidolite (Inert), Purpurite (Drags to Picks Up) and Seraphininte (Strong).
December 2013
A drop down menu was added to the Home Page to show at a glance the contents of all sections with multiple pages.
The concept of cryptic ions was introduced under the section on Yellow Tourmaline on page 2 of Tourmalines. Ions of iron and manganese can be create magnetic response in gemstones without contributing color. These ions are therefore cryptic (hidden, colorless, invisible). Cryptic ions are not only found in Tourmaline, but also Emerald, Andradite Garnet, Grossular Garnet and probably many other gemstones. At the bottom of the same page 2, an example of a near-colorless Tourmaline with strong magnetism was added. This gem illustrates how iron and manganese within a gem can strongly influence magnetic response without adding color.
An interesting example of native copper and ionic copper within a single gem (Chalcedony) has been added to the Copper section on the page titled the Magnetic Metals that Color Gems.
A paragraph about the importance of Standardized Testing procedures was added the the section titled The Floatation Method on page 2 of How to Use a Magnet for Gem Identification.
A photo of transparent Rhodonite was added to the section titled Translucent to Opaque Gems That Pick Up on page 3 of How to use a Magnet for Gem Identification.
On the page titled 10 Practical Uses for Gem Identification under Synthetic and Imitation Gems, a photo of synthetic pink Spinel vs natural pink Spinel was added to illustrate how these gems can be separated by magnetic response. Further below under the same section, a photo of natural vs synthetic Aquamarine was added as an example of gems cannot be separated by magnetic response. On the same page under Testing Gems Mounted in Jewelry, 2 new examples of cluster jewelry- a Sapphire ring and a Ruby ring- were added as examples of small gems in jewelry that can be tested with a Pinpoint Wand. Under the same section, a photo of an imitation Turquoise pendant was added to show how magnetic testing can separate imitation and natural Turquoise.
November 2013
A new 3-page report about Tourmalines titled Tourmalines: Color and Magnetism was added. This chapter can now be accessed from every page of this website by clicking on the Tourmalines link.
An example of another imitation Diamond that shows a Pick Up response to a magnet (besides GGG) was added to the page about Diamonds. The gem is an unusual Pink YAG trillion.
Under the section titled Concentration of Metals on page 2 of Overview of Magnetism in Gemstones, a paragraph was added explaining how higher concentrations of metals increase density and refractive index in gemstones. Examples of Almandine Garnet and pink YAG are given.
Photos of 3 transition metals- iron, manganese and chromium- that show their appearance when in solid metal form were added to the top of the page titled The Magnetic Metals That Color Gems.
On the page titled Separating Look-alike gems, 2 new look-alike examples were added: Ruby vs. Chrome Pyrope Garnet, and Chrome Tourmaline vs. Tsavorite Garnet.
On page 3 of Garnet Magnetism, a correction was made to show that Pyrope Garnet and Grossular Garnet are allochromatic Garnets. All other gem Garnets are idiochromatic. On the same page, a new section titled Unpaired Electrons was added to describe how the degree of magnetic attraction in gems is related to the number of unpaired electrons in the metals that color them. Examples with photos are provided.
New photos of treated gems that cannot be separated from their natural counterparts using magnetic testing were added the section titled Treated Gems on the page titled 10 Practical Uses for Gem Identification. The photos show Oregon Sunstone vs. diffused red Andesine, and dyed blue Chalcedony vs. natural blue Gem Silica. On the same page, 2 new examples of gems in jewelry- Chrysoprase and Rhodolite Garnet- that can be tested with a magnet were added to the section titled Testing Gems Mounted in Jewelry.
October 2013
A table showing 20 Diamagnetic Gems was added to page 2 of Overview of Magnetism in Gemstones. On the same page, a new photo of pale and dark Axinite was added to show how increasing concentration of iron results in increasing magnetic response. Also on page 2, a Bar Graph of 10 allochramatic gems and 5 idiochromatic gems was added to show the sharp contrast in magnetic susceptibility between these 2 types of gems.
A Bar Graph showing the relative magnetic susceptibilities of 20 types of allochroamic gems was added to page 4 of Overview of Magnetism in Gemstones.
An example of how a dyed gem (Calcite) can be distinguished from an untreated gem (Rhdocrosite) by magnetic response is presented with photos on the page titled 10 practical Uses for Gem Identification.
A video showing how orange Spessartine Garnets can by easily separated from a parcel of orange Sapphires was added to the page titled Separating Look-alike Gems.
The page titled Diamonds: Natural, Imitation and Synthetic is now presented as a separate section with a link on every page rather than as page 6 of How to Use a Magnet for Gem Identification.
A Bar Graph showing the relative magnetic susceptibilities of all Garnet species and varieties was added to page 1 of Garnet Magnetism. The link to this section on every page has been shortened to simply “Garnets”.
On the Magnetic Susceptibility Index, the range of magnetic response for Chrome Chalcedony was expanded to include a Weak response, not just Inert. Mexican Fire Opal was separated from Brazilian and Oregon Fire Opal, as Mexican Fire Opal is Inert and other locations show a Weak response. Yellowish brown cat’s eye Apatite colored by rare-earth metals was added to the index with a response range of “Weak to Strong”. As more Emeralds were tested, the response range was expanded to Inert to Moderate. As more blue Kyanite gems were tested, the response range was changed to “Inert, rarely Weak”.
September 2013
On page 2 of Overview of Magnetism in Gemstones, some new examples and new photos were added for clarification. Under Diamagnetic Gems, examples with photos of organic gems were added. Under Concentration of Metals, Chrysoprase and green Tourmaline were added as examples showing how increasing concentrations of metals result in stronger magnetic responses. Sphalerite was also added to show that strong color is not necessarily related to concentration of metals. On the same page under Valence States, Green Beryl, Aquamarine and Golden Beryl were provided as examples of how gem treatments can affect valence states and magnetic responses. Two new sections on the same page - Types of Metals and Inter-valence Charge Transfer- describe additional factors that can affect magnetic responses.
On page 3 of Overview of Magnetism in Gemstones, Larimar was added as an example of a gem colored by Copper. Brown Apatite was added as an example of gems colored by rare-earth metals. Photos of Sunset Quartz, Carnelian and Chrome Chalcedony were added to the section titled Magnetic Metals Within Microscopic Inclusions. Blue Zircon, Lapis Lazuli and Pink Opal were added to the section titled Other Coloring Agents. An new section titled Aluminum was added to this page, with examples of gems containing aluminum.
On page 4 of Overview of Magnetism in Gemstones, a photo of Paraiba Tourmaline was added to the section titled The Spectroscope in Relation to Magnetism.
Under Practical Uses for Gem Identification on page 4 of How to Use a Magnet for Gem Identification, the primary coloring agent for Spinel was corrected to show cobalt rather than iron. Photos of synthetic red and green Spinels that are magnetic were added. A new section titled Country of Origin was also added to this page to note how a magnet can occasionally be useful in determining the origin of a gemstone.
A section titled Separating Look-alike Garnetswas added to page 5 of How to Use a Magnet for Gem Identification. This section provides 4 examples with photos of Garnet look-alike pairs that can be separated using a magnetic wand.
On page 4 of Garnet Magnetism, it is noted that higher chromium content in Chrome Pyropes increases the refractive index and specific gravity of the gems.
On the Magnetic Susceptibility Index, the column showing Causes of Color was updated to include color processes such as inter-valence charge transfer, and several corrections to causes of color were made. The range of response for Emerald was broadened from just Weak to “Inert to Weak”. The Tourmaline section was re-grouped to show Tourmaline by species- Dravite, Elbaite and Schorl.
August 2013
This month saw a lot of changes to the website: new videos, photos, examples and information about magnetism in gemstones. It would be tedious to mention every change here, but the highlights are noted below.
A composite video that demonstrates the magnetic responses of Spessartine Garnet, Aquamarine and blue Topaz was added to the top of the Home page. Other videos of magnetic responses were added to page 1 & page 2 of Overview of Magnetism in Gemstones, and page 2 & page 4 of How to Use a Magnet for Gem Identification.
A video of how to scan a parcel of gems with a magnet now leads the page titled Practical Uses for Gem Identification. Information and photos of faceted doublets were also added to this page. Other practical uses with photos were also added to this page, including separating Tanzanite from purple YAG.
The page titled Separating Natural Look-alike gems was expanded to include 5 more examples of look-alike pairs. A number of new examples were also added to the Separation Chart for Look-Alike Gems.
A new page dedicated to Diamonds titled Diamonds: Natural, Imitation and Synthetic was added as page 6 of How to Use a Magnet for Gem Identification.
New examples with photos were added to the page titled The Magnetic Metals that Color Gems. A link to an excellent article about the causes of color in gems by Kurt Nassau was also added to this page. At the bottom of this page, a new section was added called Other Coloring Agents. Several examples of diamagnetic coloring agents are given in this section.
A paragraph about micro-magnetism in gemstones was added to the bottom of page 1 of Overview of Magnetism in Gemstones.
Madeira Citrine, a rare example of a Citrine that is colored by iron impurities and shows magnetic attraction, was added to the page titled Diamagnetic Gems. On the same page, new photos of diamagnetic gems were added, including Spodumene, Zircon and Kyanite.
New information for several gems was added to the Magnetic Susceptibility Index, including: blue Smithsonite, Myrickite Chalcedony Quartz, Chrysocolla Chalcedony, Madeira Citrine Quartz, violet YAG and green Amblygonite. Chalcedony was added to the Quartz section on the Index, and Bumble Bee Jasper was moved out to the Quartz section, as it is not Jasper.
July 2013
A photo of an Ethiopian Precious Opal was added to the Diamagnetic Gems section at the top of page 2 of Overview of Magnetism in Gemstones. On the same page, under Idochromatic and Allochromatic Gems, it was noted that yellow and brown Dravite Tourmalines show no attraction to a magnet. Under Valence States on the same page, Fire Opal (with photo) was added as an example of a gem colored by microscopic inclusions of iron oxide that is usually (but not always) diamagnetic. Under Magnetic Inclusions on the same page, a photo of Hematite in Quartz (Pietersite) was added as an example of magnetic inclusions.
The page titled Magnetic Metals that Color Gemstones on page 3 of Overview of Magnetism in Gemstones was entirely rewritten and expanded to include many additional photos and a more in-depth explanation of magnetic coloring agents in gems.
After testing a 5ct transparent Rhodocrosite gem, the high range for Rhodocrosite susceptibility was raised from SI 4271 to SI 5269. This qualifies it as the most magnetic transparent gemstone tested, even surpassing Spessartine Garnet. A photo of this record-breaking transparent Rhodocrosite is shown on page 3 of How to Use a Magnet for Gem Identification.
Information and a photo of Chrysoprase with Large Magnetic Inclusions was added to the Testing Magnetic Inclusions section at the bottom of page 4 of How to Use a Magnet for Gem Identification.
Magnetic testing of Chromite ore samples showed a drag response to an N52 magnet, and this info was added to the Magnetic Susceptibility Index. Chromite is not a gemstone, but it is found as inclusions within gemstones.
The Opal listing on the Magnetic Susceptibility Index was expanded to include 4 types of magnetic Opal: Prase Opal, Kiwi Opal, Fire Opal and Boulder Opal. Prase Opal, colored green by nickel within microscopic inclusions of Chrysoprase, is weakly magnetic. Green Kiwi Opal from Madagascar, colored most likely by iron oxide inclusions, is weakly magnetic. Orange and yellow Fire Opal is also colored by iron oxides, and magnetic responses range from inert to weak. Boulder Opal and Matrix Opal are strongly magnetic due to iron in the surrounding host matrix.
Charlcedony listings on the Magnetic Susceptibility Index were moved to the Quartz section, alphabetically from "C" to "Q".
Information and a photo of Dark Green Hydrogrossular Garnet (“Transvaal Jade”) was added to the bottom of page 5 of Garnet Magnetism. The green color and higher refractive index of these gems are likely influenced by higher chromium content.
June 2013
Cobalto Calcite and Cobalt Spinel were added to page 3 of Overview of Magnetism in Gemstones as examples of natural gems that contain cobalt as a coloring agent.
At the bottom of the same page 3, the section on Colorlessand Near-Colorless Gemstones was rewritten to include a distinction between allochromatic and idiochromatic gems. Colorless idochromatic gems can show a magnetic response, while colorless allochromatic gems are inert (diamagnetic). New photos of Near-Colorless Spinel and Near Colorless Fosterite (Peridot) were added.
A photo of Opaque Rhodocrosite was added to page 3 of How to Use a Magnet for Gem Identification. Just below this, a photo comparing Transparent Rhodocrosite to Pink Malaya Garnet was also added. A photo of black Onyx was added to the same page under Black Gems.
Photos of natural Red Beryl and natural Alexandrite were added to the section on Synthetic and Imitation Gems on page 4 of How to Use a magnet of Gem Identification.
The same section contains new photos of Natural vs Synthetic Ruby, and Natural vs Synthetic Emerald.
On the same page 4 under Treated Gems, a photo of Dyed Carnelian was added, as well as a photo of Beryllium Treated Ruby and Glass-filled Ruby.
At the bottom of the same page 4, a section on Testing Magnetic Inclusions was added to demonstrate how we can use a magnet to glean information about types of inclusions. Examples with photos were added to this section for Chrysoprase with Magnetic Inclusions and Calcite with Magnetic Inclusions.
A photo of a purple Color Change Garnet was added to the Color Change Garnet section on page 2 of Garnet Magnetism.
Colorless Andradite was added to the range of colors found in Andradite Garnet on page 5 of Garnet Magnetism.
Also on page 5 of Garnet Magnetism, the graph for Andradite Garnet was corrected to show Demantoid Garnet points falling along the Grossular-Andradite join rather than the Uvarovite-Andradite join. All other graphs in this website showing Andradite were similarly corrected to show Grandite composition. Below the graph on the same page, an new photo of "Topazolite" (yellow Andradite) was added. Near the bottom of the same page, the graph for Hydrogrossular Garnet was updated to show a few more graph points of newly tested samples.
On page 6 of Garnet Magnetism, a new section was added near the top of the page describing methods we can use to distinguish between red Pyralspite Garnets: Pyrope, Almandine and Spessartine.
May 2013
New photos and descriptions of 2 gems- a Diamond and a Beryl- with rare magnetic inclusions were added to page 2 of Overview of Magnetism in Gemstones.
At the bottom of page 4 of How to Use a Magnet for Gem Identification, a photo and description of dendritic Opal has been added to the section on using a pinpoint wand to test for magnetic inclusions.
Two more examples of how to separate rough stones with a handheld magnet- Spessartine from Hessonite, and Rhodloite from Spinel- were added to page 4 of How to Use a Magnet for Gem Identification.
A photo of a suite of Chrome Pyrope Garnets and a photo of a purple Pastel Pyrope from Sri Lanka were added to page 4 of Garnet Magnetism.
A Chrome Mali Garnet was tested for the first time. A photo and description of this rare gem were added to page 5 of Garnet Magnetism.
The section about Hydrogrossular Garnet on page 5 of Garnet Magnetism was rewritten, with new photos added. The section was corrected to indicate that Hydrogrossualar is never transparent and that most “transparent Hydrogrossular” sold on the market is actually Idocrase. A new Hydrogrossular graph is presented. A photo of “Watermelon Garnet” (red and green Hydrogrossular) is also shown.
Some Rhodolite and Malaya Garnet gems can look very similar. How do we tell them apart? A distinction is presented on page 6 of Garnet Magnetism.
April 2013
Under the Idochromatic or Allochromatic section on page 2 of Overview of Magnetism in Gemstones, the following clarification was added: "You can be sure that any natural transparent gemstone larger than 0.5ct that is magnetic enough to be picked up by a magnet is an idiochromatic gem with iron, manganese or rare earth elements in its chemical composition."
A strong magnetic response for brown Sphene was noted on the Magnetic Susceptibility Index, and the susceptibility range for brown Enstatite was raised to 681.
The origin of the word Pyrope is mentioned on page 2 of Garnet Magnetism : "Pyr is the Greek word for fire, alluding to the fire red color that this Garnet species is known for". On the same page, a photo of a green Color Change Garnet was added to the Color Change Garnet section.
Photos and a description of Imperial Malaya Garnet were added to the Malaya section on page 3 of Garnet Magnetism. Under the same section, findings for the composition of 2 more Masasi Bordeaux Garnets were added, as well as another photo of Masasi Bordeaux Garnet.
The Rhodolite Garnet section on page 4 of Garnet Magnetism was expanded, and photos of Cranberry Rhodolite and Raspberry Rhodolite are now shown. On the same page, the following information about Pastel Pyrope Garnet was added: "Over-sized Pastel Pyrope gems can be dark red and identical to Standard Pyrope."
On page 6 of Garnet Magnetism it is noted that a Chelsea filter can be used to separate Chrome Pyrope Garnet from Standard Pyrope Garnet.
March 2013
The Magnetic Susceptibility Index was changed to a pdf format for ease of updating. Readers may need to increase the screen view size (cntrl +) in order to clearly view the Index table.
Brown Sinhalite was added to the Index as a transparent gem that shows a strong magnetic response when floated. Previously only yellow Sinhalite (weak response) had been tested. Selenite, a variety of gypsum that is transparent, was also added to the Index (diamagnetic). Several new blog comments have been added to the bottom of the Blog page.
February 2013
Some Color Change Garnets can show up to 4 colors depending on lighting. An example with photo is provided under the Color Change Garnet section on page 2 of Garnet Magnetism.
Ten more graph points were added to the Malaya Garnet graph under the Malaya section on page 3 of Garnet Magnetism. Two more examples of Malaya Garnets with primary Spessartine content are among these. New photos are included.
Information about Garnet nomenclature has been rewritten on page 3 and under the Conclusion on page 6 of Garnet Magnetism.
Pastel Pyropes can fluoresce in daylight. This info was added to the Pastel Pyrope section on page 4 of Garnet magnetism. A photo of a large dark Pastel Pyrope was also added.
A new photo of a fine 1.8ct Tsavorite Garnet (emerald cut) was added to the Green Grossular section on page 5 of Garnet Magnetism.
The graph of Orange Garnets on page 6 of Garnet Magnetism was updated to include 4 more orange Malayas. A photo of a large overly dark red Malaya was also added to page 6.
Comprehensive information about Garnets can be found in Renee Newman’s book Exotic Gems Volume 2 (2011). This reference was added to the Garnet section on the Resources and Links page.
January 2013
For easier navigation of this website, a table of contents has been added to the top of each of the 3 major sections: Overview of Magnetism in Gemstones, How to Use a Magnet for Gem Identification, and Garnet Magnetism.
A rare near-colorless Malaya Garnet (species Pyrope) was encountered for the first time by this researcher. Information and a photo were added to the bottom of the Malaya section on page 3 of Garnet Magnetism.
A photo of a Chrome Mali Garnet (species Grossular) was added to the Grossular section on page 5 of Garnet Magnetism.
A new article by this researcher about magnetism in diamonds titled “Detecting HPHT Synthetic Diamond Using a Handheld Magnet” is published in the current issue of the Gems and Gemology journal (Winter 2012). A reference to that article was added to the Resources and Links page.
December 2012
All 6 pages of the section titled Garnet Magnetism were updated to show test results for 500 Garnet samples rather than the previous smaller set of 250 samples. Garnet composition graphs for each variety now reflect a more complete set of points, and the All Gem Garnet Graph on page 3 now shows all 500 points.
A new reference for an article by this author called “Gem Identification with a Magnet” was added to the Resources & Links page. The article appears in the Winter 2012 edition of the U.S. Faceter’s Guild online newsletter.
The following qualification was made to page 2 of How to Use a Magnet for Gem Identification: A pick up response by an orange gem is not strictly diagnostic for Spessartine Garnet, as two other uncommon Garnet varieties with high Spessartine content- Orange Malaya and Orange Color Change Garnet- also pick up.
November 2012
An orange Malaya Garnet containing Spessartine rather than Pyrope as the primary component was encountered for the first time by this researcher. Consequently, Malaya was added as another variety of Spessartine on the Gem Garnet Classification page, and a new high magnetic susceptibility of 3089 for Malaya was added to the Magnetic Susceptibility Index. The graph of Orange Garnets on page 6 of Garnet Magnetism was updated to include this Spessartine Malaya.
The low range value for magnetic susceptibility of Pastel Pyrope was lowered to 618 on the Magnetic Susceptibility Index, and the graph for Pastel Pyrope was updated to show this on Page 4 of Garnet Magnetism. A new photo showing the colors of a suite of Pastel Pyropes was also added to Page 4.
Page 6 of Garnet Magnetism now specifies that magnetic response can be used to distinguish Chrome Pyrope from Standard Pyrope, and Pastel Pyrope from Malaya Garnet. Most Chrome Pyropes and Pastels show only a Drag response rather than the usual Pick Up response of Standard Pyropes and Malayas.
October 2012
For the first time, orange Malaya Garnets were studied by this researcher, with information and photos added to the section on Malaya Garnets on page 3 of Garnet Magnetism. The Garnet Classification page was also updated to include orange Malaya as a color variety of Malaya.
A rare orange-red Pastel Pyrope was also found. A photo of this gem was added to the Pastel Pyrope section on page 4 of Garnet Magnetism
A new page was added to the series on Garnet Magnetism. Page 6, titled Distinguishing Garnet Species and Varieties, discusses how we can distinguish between Garnet species that blend in a continuous series (such as Pyrope-Almandine), and how to separate Garnet varieties within the same species when they have overlapping refractive index and magnetic susceptibility values. A section titled Distinguishing Between Orange Pyralspites is also found on this page.
The Magnetic Susceptibility Index was updated to show a new lower limit for Almandine Garnet (1926), a new higher limit for Rhodolite Garnet (1840), and a new higher limit for Malaya Garnet (2689).
September 2012
Two references were added to the Resources and Links page:
1) A 1953 paper by Basil Anderson describes his early experimentation with a hand-held magnet for gemstone separation. In this paper, Anderson is the first to show that Garnets can be separated from Rubies using a hand-held magnet. Anderson laments that magnetism in gemstones has up to that point been ignored by gemologists. If alive today, he would likely be astonished that after 60 years and great advances in magnets strength, magnetic testing is still largely ignored and un-researched.
2) Antionette Matlins devotes a chapter to using neodymium magnets for identifying synthetic diamonds in her 2008 edition of Gem Identification Made Easy.
An example comparing Rhodolite Garnet to Purplish Red Spinel was added to the Separation Chart for Look-Alike Gems.
August 2012
A photograph of a Garnet inclusion in Topaz was added to the Magnetic Inclusions section on page 2 of Overview of Magnetism in Gemstones. The inclusion causes the Topaz gem, normally diamagnetic, to show a strong magnetic response.
Identification parameters for the Pastel Pyrope variety of Garnet were added to the Pastel Pyrope section on page 4 of Garnet Magnetism.
The Gem Garnet Classification page was updated to include Imperial Garnet and Masasi Bordeaux Garnet as Trade names for brownish pink Malaya Garnet, and Maralambo Garnet as a trade name for brownish pink Pastel Pyrope.
July 2012
A chart that gives the magnetic susceptibilities for all the elements on the Periodic Table of Elements was added to the Resources and Links page.
June 2012
Two mineral that are strongly magnetic were added to the Magnetic Susceptibility Index. Pyrrhotite is a ferromagnetic iron sulfide that is commonly found as microscopic particles in Diamond. Natural Pyrrhotite crystals pick up with an N-52 neodymium magnet. Magnetite is a ferromagnetic iron oxide mineral sometimes seen in Feldspar gems. Natural magnetite crystals pick up with a magnet, and act as weak magnets themselves.
May 2012
A correction regarding Manganous Yellow Tourmaline is noted under the Idiochromatic or Allochromatic section on page 2 of Overview of Magnetism in Gemstones.This variety was referred to as allochromatic-- but it is actually idiochromatic.
A photo of all 6 primary gems that drag was added under Drag Responses on page 2 of How to Use a Magnet for Gem Identification. Under the same section, it is noted that examples of Verdelite and Indicolite Tourmaline that are pale in color may not show the drag response that is characteristic of these 2 Tourmaline varieties, which typically have strong color.
Eosphorite is another rare transparent gemstone that will pick up with a magnet. This is noted under Pick Up Responses on page 2 of How to Use a magnet for Gemstone Identification.
Low iron content in synthetic Sapphire and synthetic Spinel explains why these synthetics are easily separated from natural stones by their lack of magnetic response. See Synthetic and Imitation Gems on page 4 of How to Use a Magnet for Gem Identification.
Twelve new gemsand metals were added to the Magnetic Susceptibility Index. They are: eosphorite, cobaltitie niccolite, hercynite, native copper, bismuth, iron, opaque gray rutile, silver, gold, platinum, titanium.
April 2012
The Magnetic Inclusions section on page 2 of Overview of Magnetism in Gemstones has been expanded to include examples of inclusions in Quartz, Topaz, Oligoclase and Labradorite. Labradorite with magnetite has been added under Feldspar on the Magnetic Susceptibility Index. A photo showing a drag response at one end of a bi-color Indicolite Tourmaline was added to the Drag Responses section page 2 of How to Use a Magnet for Gem Identification. The same section now clarifies that pale-colored examples of the six primary gemstones that show a drag response (including pale Indicolite) may have chromopohre concentrations too low to show a drag response. The Gems in Jewelry section on page 4 of How to Use a Magnet for Gem Identification now contains information about magnetic Gold castings that are 14K or less. Under Pinpoint Testing Gems in Jewelry on the same page, examples of Bohemian Garnet jewelry and Turquoise jewelry have been added. An example of pinpoint testing inclusions in gemstones has also been added to this section. March 2011 - March 2012
A link to John Harris’ gem spectroscopy website was added to page 4 of Overview of Magnetism in Gemstones under the section titled The Spectroscope in Relation to Magnetism. This website gemlab.co.uk shows absorption spectrum photographs for hundreds of gems as seen through a hand-held spectroscope, and tells us what metallic coloring agents are being detected. Six transparent gemstones other than Garnet have been found to show a pick-up response to an N-52 magnet. These rare gems (Siderite, Tantalite, Triplite, Triphylite, Vivianite and Xenotime) are noted under the section titled Pick-Up Responses on page 2 of How to Use a Magnet for Gem Identification. A seventh exception to the diagnostic test for Garnet is noted on page 3 of How to Use a Magnet for Gem Identification under the section Translucent and Opaque Gems that Pick Up. Rhodcrosite is generally regarded as a translucent to opaque gem, but on rare occasions, completely transparent gems are found. New information on how to distinguish natural Hematite from synthetic Hematine using weaker magnets is provided in the section Metallic Cabs and Minerals on page 3 of How to Use a Magnet for Gem Identification. The section titled Synthetics and Imitation Gems has been greatly expanded on page 4 of How to Use a Magnet for Gem Identification. More gemstone examples are provided, including separation of natural Alexandrite and natural Sapphire from their synthetic versions. A new section titled Treated Gems has also been added here. The section titled Gems in Jewelry has been re-written to include the Pinpoint Testing method on page 4 of How to Use a Magnet for Gem Identification. Information on Titanium jewelry is also added.The section titled Diamondshas been expanded on page 5 of How to Use a Magnet for Gem Identification to give more information on the usefulnesss of magnetic testing to separate natural and synthetic Diamonds. Under Separating Look Alike Gems on page 5 of How to Use a Magnet for Gem Identification, Chrome Tourmaline and Verdelite Tourmaline have been added.Quite a few new gemstone types have been tested and added to the Magnetic Susceptibility Index. Additions include: Alexandrite, Synthetic Alexandrite, Synthetic Diamond, Synthetic red Beryl, Synthetic blue Beryl, Synthetic red Beryl, Chondrodite, black Jadeite, Gadolinite, Lazulite, Nuumite, Siderite, Smithsonite, Triphylite, Triplite, Tugtupite, Vivianite, Wulfenite, Xenotime. The graph titled All Gem Garnet Compositions on page 3 of Garnet Magnetism has been updated to show expanded ranges for Pyrope (new high), Demantoid (new low) and Mali Garnet (new low). The Magnetic Susceptibility Index has also been updated to show these expanded ranges. Composition information on JTV’s Masasi Bordeaux Garnet™ has been added to the Malaya Garnet section on page 3 of Garnet Magnetism. A newly published paper titled “Determining Garnet Composition from Magnetic Susceptibility and Other Properties” by D.B. Hoover has been added to the Resources and Links page under Garnet References.Renee Newman's latest bookRare Gemstones (2012) is the first book to list magnetic response as one of the identifying properties for transparent gemstones. Magnetic information for specific gems is drawn from this website.The Gemology Tools Professional software program called GTPro now includes magnetic response as one of the identifying properties in its extensive index of gemstones. -------------------------------------
What's New?
Sapphire
This page provides a quick way to find out what’s new in gemstone magnetism. Since the launching of this website in the Spring of 2011, new information and updates have been incorporated into the text. The locations of these updates are noted below. All future changes and additions each month will be noted on this page.
June 2016
A second large Uvarovite Garnet crystal was tested for composition, this rare crystal from Finland. A photo,
composition graph and information on magnetism were added to the Uvarovite section at the bottom of page 5 of Garnets.
May 2016
A photo of a large12.52ct blue Paraiba-type Tourmaline from Mozambique was added to the Blue color variety section on page 3 of Tourmalines. The color is due entirely to copper, but this Tourmaline is strongly magnetic due to high manganese content.
April 2016
Additional photos of a dark green Verdelite pear, a light green Chrome Tourmaline oval, and a brownish
green Chrome Tourmaline round were added to the Green section on page 1 of Tourmalines.
On page 3 of Tourmalines under the Pink and Red section, we added a photo of a Rubellite pear that was erroneously sold as a copper-bearing Tourmaline.
March 2016
A photo of a pure red Almandine Garnet without purple hues was added to the Almandine section of page 2 of Garnets.
On page 5 of Garnets: a new photo of a light green Grossular was added to the Green Grossular section, a new paragraph with 2 new photos of near-colorless Grossulars were added to the Near-colorless and Leuo Garnet section, and a photo of a yellow Hessonite was added to the Hessonite section.
Under the Gem Shape and Cut section on page 3 of How to Use a Magnet, a new paragraph was added with photos of Peridot showing how the irregular shapes of rough stones and the pavilion side of gems can decrease magnetic response.
To the Magnetic Susceptibility Index, man-made Moissanite (Diamagnetic) was added, as well as Near-Colorless and Leuco Garnet (Weak to Moderate).
February 2016
A yellow Pastel Pyrope Garnet that we newly discovered was added to the Pastel Pyrope section on page 4 of Garnets. This unique gem is the only Pastel Pyrope with yellow daylight color that we’ve ever encountered, and a photo and discussion is included.
A Color Change Garnet with unusually high brilliance and dispersion similar to Andradite Garnet was added (with photo and discussion) to the Color Change Garnet section on page 2 of Garnets. This is the only Pyralspite Garnet we have ever encountered that shows high dispersion.
On the Magnetic Susceptibility Index, Pietersite was moved from the Quartz (macrocrystalline)
category to the correct category of Chalcedony (microcrystalline Quartz).