Gemstone/mineral magnetism

This is an excellent site on the use of meodynium magnets to determine what you may have or not have in gemstones and/or minerals. More for gemstones since you lose many identifying features after faceting. Easy to understand and all it takes is a $6 magnet . Some of the results are great and work for many stones that get misrepresented or sold as fakes....like aquamarine vs. blue topaz, tanzanite vs. iolite, synthetic spinel vs. natural spinel, etc.
[gemstonemagnetism.com]

Awesome stuff! I'm going to experiment when I get home!

Thanks for the link Jason, extremely interesting - as Ken, I'll be experimenting!

Really fascinating - I found that apparently iron-rich boracite is moderately strongly attracted, and chambersite even more so. I also found a misidentified cut gem in my collection. (Color-change garnets are strongly attracted - much more so than color-change sapphire - proving the true identity.)

Awesome..so it worked on that, Ken. I had never known that something as simple as magnetism could be used the layperson to help identify stones. Sure some will be more difficult like the ones that are "moderate" as they overlap to ""weak" and "strong" but many things like the garnets can be easily distinguished...especially Demantoid....which it says actually can be pulled upwards by a magnet...I will need to try that one sometime

Hi Jason,

Very interesting reading material. This subject has sparked my interest in experimenting with some applications to minerals that contain REE etc. Interesting subject. Like the flotation idea to observe reactions.

Cliff

Place the end of a 20cm length of video tape between two 1x3x6cm neodymium magnets and fasten the other end to a shelf. The video tape twists easily and provides a very small restoring force. Let the magnet orient to north then glue a one cm square mirror to the magnet. Bring a mineral containing paramagnetic metal (especially iron, copper, or manganese) near the magnet and it will twist. If a light is directed at the mirror, a small displacement of the mirror will result in a large movement of the spot of light across the room. The gem or mineral does not need to move, the magnet does. There are a few iron, copper, and manganese minerals that do not cause a reaction (pyrite, chalcocite, romanechite).

A reference for magnetic suseptiblity is : USGS Open File Report 99-529, Magnetic Suseptibilities of Minerals by Sam Rosenblum and Isabelle K. Brownfield.

I used a stack of RE magnets that are pretty powerful, but much less so than the large single one that the website recommends. Still, I was able to pick up small almandines, demantoids, spessartines, and chambersite. I did play with the floatation method, but it was fun to see transparent orange spessartines sticking to the magnet so well that they are hard to shake off!

Glad to see so many people are visiting my website gemstonemagnetism.com. Thank you Jason for posting the link. Everyone who works with gems owes it to themselves to become familiar with using a magnet for gem identification. And yes, its actually fun!

I have been experimenting with the RE magnet and some garnet sand I panned long ago in Sabino Canyon near Tucson. Indeed, the magnet nicely picked up all the garnets and rejected the stray grains of quartz. My sample had been pre-cleaned of magnetite, etc. with a strong Alnico magnet, so the RE magnet provides a really slick way of concentrating the garnets and leaving behind any dark bits not so strongly paramagnetic.

Shades of Cavendish! Don Peck's device could easily be upgraded to pretty high sensitivity using a laser pointer. It would be interesting to see if a "strongly" diamagnetic substance such as bismuth could move the spot.

Magnetic response of many antiferromagnetic minerals at room temperature will depend on whether the Neel temperature is above or below room temperature. A few minerals that are antiferromagnetically ordered at room temperature would be expected to have rather low magnetic responses; among these would be minerals such as goethite and chalcopyrite. Hematite with its canted antiferromagnetism has a small parasitic ferromagnetism from incomplete cancellation of magnetic moments above the Morin transition.

Ideally, pyrite is diamagnetic because of its content of low-spin ferrous iron; however, slightly oxidized pyrite has acquired a coating of paramagnetic szomolnokite (as shown by Moessbauer spectroscopy). Powdered pyrite would, therefore, be expected to exhibit the paramagnetism of this ferrous sulfate monohydrate unless it had been carefully protected from oxidation.

I was once visiting with Brian Lees of Collectors Edge in Denver and he showed me some 5gallon buckets of Benitoite gravel that he said he had purified with rare earth magnets from the concentrates of his washing/screening operation when he was running his Benitoite mine in San Benito Co. California. Looked to me like he had several years worth of cutting material for a cutting factory in India or China. A huge amount of work and additional expense in addition to a lot of time, effort and money to further process it into very small gemstones. Even if he had gotten the stuff for free, this I think would not be hugely profitable.

Rock Currier
Crystals not pistols.

Hi All,

seems quite a nonsense to me. E. g. synthetic and natural Spinell are the same substance. How can there be a difference in magnetic properties. With a magnet You can attract Magnetite, Pyrotine, Hemoilmenite, native Iron and may be some other, very rare minerals. A small content let´s say of Magnetite in a stone only in an extraordinary case can be an indicator that this stone is natural.

I have worked many years with Rare Earth-Magnets used in technical equipment; and I am collecting minerals for many years. I am quite astonished.

Greetings from Goslar

Georg

Synthetics are identical to natural gems only as far as major chemistry. Minor chemistry is distinctly different. The types and amounts of coloring agents used in synthetic spinel and other synthetic gems can be different from natural gems. This will be evident to anyone who uses an N-52 magnet to test gemstones. The majority of synthetic gems are not attracted to a magnet, probably because the concentrations of metallic chromophores used in labs are too low to be detected. Synthetics that are attracted to a magnet are listed on the Magnetic Susceptibility Index. The multitude of micro inclusions in natural gems also results in minor chemistry that is different from synthetics, but this does not affect magnetic response, except in rare cases.
Kirk Feral

As far as natural vs. synthetic gems, I recall reading that synthetic diamonds may be magnetic (due to inclusions and impurities from the manufacturing apparatus), while natural ones are never so. I tested this with a batch of yellow synthetic diamonds, and it is true - about a third are pretty strongly affected. Yes, these are real diamonds, and no, none of my many natural real diamonds show any effect.