20 May 2008
Why all the hoopla over that curious copper color?
And why is Oregon Sunstone Labradorite so very, very special?
It is my experience that you can tell how well a student understands the subject being taught based on the questions they ask. And given the questions that we are receiving about the Oregon Sunstone Labradorite issues, I can tell that there are a lot of people who really don’t understand exactly how all of this plays out regarding copper and the feldspars. So I thought that this week we would take a look at this curious copper color and why there is so much hoopla over the issues.
ISGFirst, let’s take a look at the most simple type of copper coloration in a gemstone. At left you see native copper, the metal that U.S. pennies and water pipes world wide are made from. This is what it looks like coming out of the ground. But if you take a close look at the image (as well as the banner image at the top of the page) you will see some green color patches forming on our native copper. This is oxidation.
ISGThe mixing of the copper with oxygen causes the copper to expand and get all bubbly due to the oxidation as you can see in the image at right. When copper oxidizes it turns green and eventually bluish green in color, and forms what appears to be the bubble formations known as botryoidal formation that we see in malachite. And the image at right is indeed malachite, an oxidation of copper as we saw above that can be cut and polished into the beautiful gemstone that you see below.
But this is a very common gemstone formed by the actual copper itself. Much the same as azurite and turquoise are both combinations of copper and other elements forming into a single massive formation.
But what about the Oregon Sunstone Labradorite? What makes it so rare and different? Well, in the Oregon formations the copper is not a prime ingredient of the feldspar, but instead an inclusion. An impurity. So rather than the copper forming the gemstone, it is the cause of the color in the gemstone, and by virtually all of the textbooks it is effectively the only place on earth you can find copper as a coloring element in labradorite feldspar. And not only that, the result of the copper in the Oregon Labradorite formations produces gemstones that are unique in the world of gemology.  ISG
At left you see a slide show of increasing magnification where the copper grains inside the Oregon Sunstone Labradorite create the shiller effect, and as you increase the magnification you can actually see the minute grains of copper inside this Oregon Sunstone Labradorite.
But it gets better. In an exceptionally rare occurrence, the copper is extremely small in the feldspar and rather than occurring as a shiller effect in the stone as we saw at left, it actually imparts a remarkably beautiful solid red and/or green color to the labradorite.  Why two colors? This is because copper has what is called multiple valences. Meaning that it can form more than one type of bond with other elements to form different types of molecules. Sort of like when you hold both hands with one person you form a group of two people. But when you hold one hand each with two other people, you form a group of three people. This is one of my now famous (or infamous to the science geeks) grass roots explanations to help you understand that just like you holding hands with one or two other people will create different types of groups, copper can do the same with other elements, which is how the Oregon Labradorite can offer the different colors due to different types of copper bonds. And I know that the techies will have fun with that one.
But in truth, this is very much how it works. And when it does it is not only beautiful, but quite rare and valuable.  Below are photographs of the red and green rough, and a beautiful faceted Oregon Sunstone Labradorite from the Desert Sun Mining website.
So what we have is a very rare, very beautiful and very valuable gemstone that is native to Oregon in the United States . But there are many types of feldspar out there, and some gemstone dealers in places like Thailand and China know how to do some pretty creative stuff to make cheap gemstones look like expensive gemstone, and then pass them off for the real thing. So what if someone could take a cheaper and more plentiful form of feldspar such as an oligoclase (as seen below left), cook it up and infuse it with some form of copper to make it appear to be the far more rare and expensive Oregon Labradorite, even though it was not the Oregon material? (as seen below right).
It might look like the real Oregon Sunstone Labradorite. But it would actually be a much cheaper result of artificial color treatment of the stone, and would require that buyers be properly informed about the treatment to understand that they were not getting the real thing. But would the treaters do that? Or would they try to claim that they had found yet another very rare formation just like the Oregon Sunstone Labradorite, but in some far off place like the Congo , Mongolia , Tibet or other hard to reach spot. And if the Thailand or Chinese dealers did this, what might the story sound like, and how could we identify the treatment so we could separate it from the real Oregon Sunstone Labradorite? Maybe we could take a stone from the Congo and have a lapidary cut the ends off so we could transmit a light through it and see the infusion boundaries. Or perhaps run more Raman scans to get even better and more accurate results.
We are going to bring you the rest of this story next week.  But for this first part I wanted to lay the foundation of this issue regarding the Oregon Sunstone Labradorite so you could understand the background to the issues. Next week we will finish the saga of this curious copper color in feldspar gemstones.
Robert James FGA, GG
President, International School of Gemology

©2008 International School of Gemology . 

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