A Rare Gemstone Inclusion: Beauty In the Eye of a Rio Grande Gemologist

In this article, Chris Hoffman from the our gemstone team gives you an inside look at being a gemologist at Rio Grande.

Last edited: 4/19/2019
A royal purple, AAA-Grade round faceted amethyst
A beautiful, royal purple, AAA-Grade faceted amethyst available at Rio Grande.

Gemstones are gorgeous. And, as a gemologist, I can tell you they're even more beautiful inside—at high magnification. My name is Chris Hoffman I'm a member of the Rio Grande Gem Source team, and I can also tell you that the life of a gem geek at Rio is special and, oh, so cool. One of the many things that my teammate, gemologist Shannon Demoulin and I spend much of our time doing is examining, identifying and assessing the gemstones delivered to Rio to ensure that we—and ultimately, you—are getting the quality gemstones we pay for. We see thousands, heck, tens of thousands, of gemstones every year. Rarely does a week go by that one of us doesn't turn to the other and say, "Hey check out this cool inclusion…"

We have seen twinning, which occurs when some of the mineral crystals that form to create a given gemstone grow together in symmetrical fashion with a shared crystallographic direction, but have parts that grow in a reversed, mirror-image orientation. Under the cross-polarizing filter, we've discovered examples of Brazil law twinning, a form of twinning that finds the right- and left-hand structures combining into a single crystal. We've zoomed in on zebra stripe (also called "fingerprint" or "feather") inclusions created by the intrusion of liquid into the forming crystal. We've come across two- and three-phase inclusions and negative inclusions (which are empty spaces, or cavities, within a crystal). We've enjoyed finding bull's-eyes and Airy's spirals (which appear sort of like pinwheels inside surrounding rings)—uniaxial optic figures that are found only in quartz.

An example of a zebra-stripe inclusion in an amethyst and a needle inclusion of hematite
Left: An example of a zebra-stripe inclusion in an amethyst [image taken by Barbra Voltaire; courtesy of The Gemstone Project. Right: The needle inclusion of hematite we found within the amethyst gemstone shown above; the image was taken at 60X magnification—awesome, isn't it?

Until this week, though, we had never seen (except in books) hematite needle inclusions inside an amethyst. I don't know how many amethyst gemstones the two of us have seen this year, but I would guess it's somewhere in the neighborhood of 3,000—5,000. So, we're sitting there, we two, examining stones as we so often do, when Shannon turns to me and says (literally), "Hey, check out this cool inclusion!" When I saw it, I agreed—we just had to share it with other stone geeks out there who would, like us, excitedly admire this rare anomaly. And sharing this find has been so much fun for us that you should look for us to share more fun, interesting and out-of-the-ordinary oddities that we come across in the future!