Geology And Geophysics

The Chemical Components of Diamonds



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The World of Gems

My husband and I are appraisers. We have been into antiques and collectables for some time now. I know a lot about pottery and several other items, but neither of us knows anything about gems. We thought that as a part of our appraising that at least one of us should know something about gems. So it was I that took on this task with much enthusiasm. I had no idea that when I entered the world of colored gems that there would be much more to learn than I bargained for.

Firs, one must learn there is a hardness system to the earth's materials in what gems are formed. The most widely used is Moh's system that goes from 1-10, with 10 being the hardest. As you have guessed, diamonds are scaled as the hardest. The harder the material, the better to make a piece from it that will stand the test of time and wear. There are over 2400 minerals, but only about twenty are commonly used as gemstones in jewelry.

Most gemstones are formed in a crystalline arrangement with constant chemical composition and optical properties. These arrangements seem fantastical to someone who never knew about this or saw them. There are seven crystal forms in gems. This is how many of them grow. Others are amorphous and just grow anywhere in any form, such as opals. Some stones have what is called cleavage, which is a natural plane of weakness within the structure. Oddly enough, diamonds have cleavage though they are hard.

The most important factors classifying a gemstone are:
Color, durability or hardness, rarity, fashion, portability (can it be hidden easily) and, of course, beauty.

Members of a group are called species and the different kinds within that are called varieties.

Diamonds, sapphires and rubies come from a substance called corundum. These beauties have what our teacher calls a hard life. They are squeezed, pressed and squished beyond belief and then form into these crystal shapes far below the earth. Since other substances are in the earth, these stones pick up some of them in their growth. All gems have other trace minerals in them and that is why it is difficult to get any gem that has no inclusions. That's what inclusions are in stones. They are tiny bits of substances such as magnesium, liquids and at times gases. Some gems, like emeralds, have more than others.

Then there is the quartz group, which includes rock crystal, amethyst, peridot, jadeite, apatite and others.

The garnet group is filled with many beauties. . Did you know that garnets come in every color except blue? So, if you think your birthstone is boring, think again. You have your choice of color, unlike most birthstones.

Beryls are aquamarine (which may be the clearest of all gems) and emeralds. Emeralds are the one that contains liquid, gas and solids. It is very difficult to find one that is almost inclusion free. I love the trapiche emerald, which is from Colombia only, has a dark core and six legs of carbonaceous shale in between. The design is beautiful and it is pretty rare.

The feldspar group includes labradorite, amazonite, rhodocrosite (looks like bacon), Lapis-lazuli, opal, malachite, turquoise to name just a few.

There are gems that come from organic materials that you know as pearls, coral, amber, jet and ivory. Then there is obsidian, which is natural glass and moldavite from meteors.

Learning where they all come from, how they were formed and how to tell what it is happens to be a complicated task. Some gems can be identified immediately by the inclusions. The one that comes readily to mind is the demantoid garnet, which is green and comes from Russia. When looking through a microscope one can see inclusions that resemble horsetails. This is a sure giveaway.

Shall we say that this is only the tip of the "ice"berg in learning about these beauties. One has to learn their phenomena; their brilliance and fire, where they are from, the treatments gems undergo before you see them in a store, and naturally, learning how to tell them from some very good synthetics. There are some varieties being found still, but these are unusual and rare. When you see jewelry now, you can admire more than its beauty, you can appreciate where, how and what these wonderful items of nature went through to get to the public.



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