The Colombian Emerald Mine: More Than Just Emeralds

When you think of mining, you obviously think of the mines themselves. A coal mine or gold or silver mine are probably the first types to come to mind. Gem mines might come to mind next. Basically they’re all excavations in search of specific mineral or resource. And it goes without saying that successful mines find what they‘re looking for. Most of us probably assume a given mine just digs up whatever that is and there’s not much else to it. Without knowing much about minerals or mining, that’s probably a natural assumption. But it would be a wrong one.

So the question is then, what else do they find? Since this is mostly an emerald blog, we’ll take a closer look at what else might be found in a Colombian emerald mine. This won’t be a complete examination; instead we’ll just take a look at some of the more interesting things. I should also point out that the same gems or minerals found in a Colombian emerald mine may not be found in emerald mines elsewhere in places like Brazil, Zambia, or Pakistan, for example. One can think of the earth in these mining areas as a big mineral cocktail. And just like any cocktail you might order up at your favorite bar, the ingredients used have an effect on the end results. Throw another mineral into the mix in a gem mine and the results there may be different as well. The difference may be in the formation of other mineral types (including gemstones) and/or differences in the quality, characteristics, or formation of these minerals and gems. This helps explain why Colombian emeralds are much greener, more desirable, but also more included than their Brazilian, African, or Asian cousins. It also helps explain the existence in the emerald mines of some of the other minerals and gems I’m about to mention.

The first mineral I’ll talk about is what prompted me to write this blog. Have you ever heard of Colombian Euclase (pronounced YU-CLAZE)? Unless you’re a mineralogy buff or rockhound, I’m guessing probably not. Euclase is found in many places in the world, but it’s not often found to be of gem quality quite like it is in Colombia and Brazil. Colombian and Brazilian Euclase is highly regarded because of the beautiful blue color they possess. Euclase can also be found in yellowish, clear, and green variations in places like Austria, Brazil, the United States, Russia, Africa, among others. Quite often it is left in its crystal form still protruding from a piece of rock and bought by mineral collectors. Part of the reason for this is the difficulty in cutting the crystal to be used as a gem. Euclase has cleavage planes that intersect in its crystal structure and these planes can be a difficult obstacle for the inexperienced and unknowledgeable gem cutter. However, when done properly, cut Euclase is highly regarded and often sold at prices similar to those of good quality emeralds. Embassy Emeralds is one of the few places anywhere you will ever see cut Euclase available to purchase. The Euclase we carry all comes from the famous Chivor mine in Boyacá Department, Colombia.

Another mineral which is found without exception in a Colombian emerald mine is Pyrite. You might have seen this before and called it Fool’s Gold. It has a gold-like color and metallic appearance but has a crystalline structure that can be easily broken and crumbled in the hand. Pyrite is a very common inclusion found in Emeralds. If you have a particularly transparent emerald with a pyrite inclusion, you can often take a closer look at it with a loupe or magnifying glass. Pyrite isn’t worth much, if anything, but occasionally pyrite forms in the presence of a fossil and can replace the fossil material in its formation. What remains is a replica of the original fossil made of pyrite. This same fossil replacement process also may occur with emerald. Typically these fossils are the shells of mollusks lost in the earth and dating millions of years old. These mineral-replaced fossils are rare and valuable and often end up in private collections or museums.

Though not as common, apatite is another interesting mineral found in Colombian emerald mines. Specimens we’ve seen personally have been a light pink color, however the mineral apatite can be found in several colors such as: clear, black, blue, dark green, yellow, pink, red-brown, and purple. The variations in color are due to the make-up of the ‘mineral cocktail’ I mentioned earlier and other geological conditions under which it forms. The term apatite is actually a general term that is used to describe three subtypes of apatites named for the predominance of fluorine, chlorine, or hydroxyls. These subtypes are: Flourapatite, Chlorapatite, and Hydroxylapatite. Gem quality specimens can be cut as gems or cabochoned, however they rate as a 5 on the Moh’s Scale of Hardness making them a poor choice in terms of durability. Some apatites may exhibit the ‘Cat’s Eye’ effect known as chatoyance.

Quartz is the second most common mineral in the earth’s crust, so it’s a very likely find in an emerald mine. Like pyrite, quartz is a very common inclusion found in emeralds. Often these inclusions are tiny grain sized crystals that formed inside the emerald crystal. Quartz can be found in a variety of colors and types and some of these different types are even used as gemstones, such as Citrines, Amethyst, Jasper, and Onyx. However, most quartz found in emerald mines will be of the typically clear or white variety and you wouldn’t find them particularly useful for much of anything.

Another very common mineral found in emerald mines is calcite. Calcite is mostly white or clear and is a relatively soft mineral that is the main ingredient in the composition of sea shells, plankton, some sponges, and limestone among other things. You’ll often find calcite in veins near hot springs or in the form of stalactites and stalagmites in caves. It can be dissolved in ground water and tends to be carried with it to later form a sort of cement around other minerals and rocks, bonding them together. You might think of it as a mineral glue of sorts, holding rocks of varied composition together.

Belonging to the feldspar group, a mineral group that makes up the most common type of material in the earth’s continental crust, is Albite. Its name comes from the Latin Albus which describes its white color. Aside from being brittle and plentiful in an emerald mine, it’s a rather uninteresting mineral.

Those are some the more noteworthy or at least common minerals to talk about in an emerald mine, but there are many others. Dabbling with minerals and mineralogy can be an interesting endeavor but a daunting one if you’re someone who has to know everything there is about a subject. There’s just too much to learn. But as you can see, if your focus is limited as it is in this blog, it’s manageable and you won’t have to absorb a college geology department worth of reference books.