Emeralds: the mint green birthstone for May

Ever since I decided to attach a blog to my website, I’ve had this desire to write about birthstones. It seems perfect. Pretty-shiny gemstones, human interest, geology, geochemistry, all the drama of international finance and trade wars! There is always one problem: what to write about. Last month, I thought I would write about diamonds. That went well….

“Mom, I’m going to write about diamonds this time!”

“Great, what are you going to say about them?”

“Well, I was thinking that I would talk about covalent bonding, and how carbon bonds to make diamonds! And I could talk about graphite and how the bonding structures are different!”

“Umm…. Do you think people would relate to that?”


A sigh, “Why don’t you write about the diamond trade and blood diamonds and diamond monopolies?”

“Because covalent bonding is more fun?”


And so it went. I ran out of time on diamonds before working out what to say. So this month I decided to try again but write about emeralds. I’ll work out diamonds next year.

“Mom, I’m going to write about emeralds. I was thinking of focusing on their crystal structure and showing how ring silicates form bonds!”


“Not good?”

“Who’s your intended audience for this project?”

So, I decided to skip silica tetrahedron bonding this time too.

The birthstone for May is emerald, a rare and expensive bright green gemstone. Emeralds have been valued and mined in various parts of the world (Egypt, India, Columbia) for at least 3000 years. Today, most emeralds are mined in Columbia. But when I was doing research for this blog I discovered that emeralds are also mined in North Carolina! One of these days I’ll have to go rock hounding in North Carolina: rubies, aquamarine, emeralds, quartz and many more…. From Nevada, North Carolina is a little far for a day trip though!

Nice emeralds are hard to find and expensive to buy. Like many gemstones, emeralds are judged by both their color and clarity. There are many green gemstones (tsavorite and grossular garnets, chrome diopside, jade, tourmaline, peridot) but perfect emeralds are unique for the slight blue hues in the green. Peridot on the other hand, has definite yellow hues in the green! Emeralds are in the beryl family with a chemical formula of Be3Al2(SiO3)6, just like aquamarine. The difference in color comes from trace amounts of chromium and vanadium in the emeralds, and iron in the aquamarine.

Perfectly translucent (like looking through glass or clean water) emeralds are extremely rare. Most emeralds are full of inclusions, or microscopic cracks that make them cloudy and somewhat delicate. The inclusions are filled with other microscopic material trapped, like a fly in amber, when the crystal formed. Unlike diamonds, emeralds are graded on how they look to the naked eye.

Because of their fragility, inclusions, and relative rarity, there are a lot of treatments done to improve color and translucence of emeralds. Opticon is a type of resin that is poured over emeralds to make them harder, darker in color and more translucent. Cedar oil (from the tree) has been used to do the same for hundreds of years. All the treatments are hard to see once they are done, and most emeralds (including mine) are oiled. Most reputable dealers won’t sell emeralds treated with Opticon as it’s a little controversial. It would be like me coating one of my wood boxes with a thick layer of verathane – everything is sealed and protected but at the price of the beauty of the wood. I oil my boxes too.

I have several sets of emeralds for sale in my shop, set in both sterling silver and 14 kt gold. They vary in clarity but I have selected and set emeralds with excellent color! Come shop! And if you want something specific or special, please let me know.

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