Unscrambling a Gem of a Mystery

A new method can pinpoint which mine an emerald came from.

Hidden inside every shiny green emerald is a geographical mystery.

Once an emerald is plucked from a mine in its home country and turned into a piece of jewelry, it can be nearly impossible to figure out where the gem came from in the first place. Now, researchers from France think they have found a solution.

A new method can pinpoint what mine this uncut emerald came from.

It’s all about the water. Molecules of water are trapped inside tiny channels in every emerald. Water has the chemical formula H2O. This means that each molecule of water is made up of three atoms: two atoms of hydrogen (H) and one atom of oxygen (O).

There are several types of hydrogen atoms. One unusual type, called deuterium, weighs twice as much as the type of hydrogen most commonly found. Some water molecules contain the heavier form of hydrogen instead of the lighter one.

It turns out that when you shine a special kind of laser light on an emerald, the heavy hydrogen reacts differently in emeralds from different parts of the world. This signal reveals where a certain emerald came from.

So far, the researchers have used their method to trace emeralds to 10 specific mines in seven countries. They can also tell the difference between natural emeralds and human-made ones.

Emeralds from some countries cost more than others, so the new technique might help jewelry sellers determine how much their gems are truly worth. It could also help historians trace ancient trade routes.

So, every gem carries its own story, and researchers are starting to translate it into a language that we can all understand.—E. Sohn

Going Deeper:

Goho, Alexandra. 2003. Gemstone geography: New technique discerns emeralds’ beginnings. Science News 164(Dec. 13):371. Available at http://www.sciencenews.org/20031213/fob1.asp .

The emerald is May’s birthstone. You can learn more about birthstones at www.earthsky.com/Features/Articles/birthstones05.html (Earth & Sky).

You can learn about emerald mining in Colombia at www.emeralds.com/ (Delta Bravo).

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