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Ask A Gemologist - Species

“There are over 3,000 known minerals. About 150 gem minerals. They are classified as: Group, Species, and Variety.” For example, “Can you identify the green stone now on the screen? Remember, there are a lot of possibilities.”

Recently, I was invited to do a presentation on gemstones for two local North County San Diego clubs; Treasure Seekers of San Diego, and the Temecula Valley Prospectors. Their principal hobby is panning for gold. However, some dabble in mining gemstones. We had enthusiastic audience decidedly interested in learning more about gemstones, a proverbial “gold mine” for educators if you will.

So, we dipped our fingers into some gem identification, discussed possible treatments, and reminded them to always suspect glass or plastic when they found something. I popped up a slide, gave them a few clues then asked the audience to identify the stone. Thankfully, this technique involved no awful smells from the use of refractive index liquid.

The crowd loved the challenge. The photo examples were the best of the best quality of a particular species. The first stumper was a beautiful sunstone. The audience got into it; they called it everything but  . . . garnet, ruby, glass, tourmaline, agate, and many other things. So, to establish a common language we began with some fundamental terms.

Karat vs Carat? Karat designates the purity of gold. In gems one carat equals 0.2 grams or 1/142 of an ounce. “Did you know you could mail 142 one carat diamonds in the mail for 49 cents? Now, you might want to include some insurance on that!”

“Can you name some organics?” Amber, pearl, shell, “Excellent!”

“What is commonly used to imitate gems?” Glass and plastic.

“What is a synthetic?” A gemstone made in a laboratory. Essentially it has the same physical, chemical, and optical properties as a natural stone.

So, it was back to a green stone now on the screen.

“Emerald,” they shouted. “Correct. What is the species?”

Then with a click of the mouse pointer the word “Beryl” appeared.

“Did you know emerald and aquamarine are beryls, the same species?” 

This caught their attention. Species? As a presenter you can never really anticipate what word or term will trigger questions. Well, to be honest, it was probably the photo of the beautiful emerald ring on the screen.

“Emerald and aquamarine are essentially the same mineral. However, iron provides the color for aquamarine. Chromium, within the structure, makes the emerald green,” I said.

Then the real question surfaced, “If they have the same chemical structure, why is one so cloudy looking and the other is so clear?”

Simultaneously, the following thoughts ran through my mind:

Beryl is a mineral of beryllium aluminum silicate, forms in the hexagonal crystal system, and has a chemical formula of Be3Al2(SiO3)6. Beryl commonly forms in pegmatites, but also occurs in mica schists in the Ural Mountains, and in limestone in Colombia.

No, that won’t help  - you’ll just lose the audience, too technical.

Then it hit me, “Different growth environments create different inclusions that distinguish the two. Emeralds typically are heavily included, then oiled to hide the fractures, aquamarines are not.”

Now we had the perfect lead-in to talk about how inclusions can separate natural from synthetic emeralds, glass, and plastic.

“Inclusions, mother nature’s fingerprint, are the very thing that separates your gem, a product of nature, from a synthetic made in a laboratory. Always check for gas bubbles first. They usually look like little donuts. But that’s another presentation.”

Limited to 30 minutes, there was no time to talk about the other beryls: heliodor, or golden beryl, goshenite, colorless beryl, red beryl, and morganite, pink beryl.

However, this provided the perfect opportunity to introduce GIA’s Gem Encyclopedia as a free online resource for gem enthusiasts. If you haven’t seen it take a look. Simply go to gia.edu.”

After many questions, my presentation ended with a quote from the Handbook of Gem Identification.

“One who seeks to become proficient at Gem Identification must guard against the failure to consider all possibilities.”  - Richard T. Liddicoat, Jr.

What a fun evening. After the event people swarmed me with questions;

“How can I learn more?”

“Where can I go if I’m not sure of what I’ve found?”

“Would you be willing to speak to our group? . . . ”

Suddenly, it was as if Mr. Liddicoat was speaking to me from beyond, “Remember Patrick, the failure to consider all possibilities has another meaning - it’s the people, the living gems, who make working in the jewelry industry rewarding and fulfilling. You know the species - Homo Sapiens.”

(This post appeared in Winter 2014 edition, WJA News San Diego)
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Location: Vista, CA, USA

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