What are the different types of gemstones? Category of Gemstones - There are several different types of gemstones, and a good knowledge of the different categories can help a collector or enthusiast greatly expand his or her repertoire. Some gemstones are so special in chemical composition and transparent structure that they fall into their own category, although others can be collectively grouped into one. Here are the main types of precious and semi-precious stones: Diamond: Diamond is a type of precious stone and is quite well known for being the hardest in nature. Diamonds are largely high-carbon crystals that have been melted at maximum pressure and temperature. Diamonds themselves are not particularly rare: thousands are mined around the world every year; However, high-quality huge diamonds are extremely rare, and it is these that are well known for characterizing diamond standards as the most valuable gemstone in the world. Corundum: This is the second hardest type of gemstone and is widely defined as silent of aluminum oxide and many trace elements. Trace minerals create various types of corundum, and probably the two best-known examples of this type of stone are sapphires and rubies. Rugged corundum is not used like gemstones, but is used as an industrial strength abrasive element due to its hard nature. Chrysoberyl: This is the third hardest type of gemstone, and although it uses aluminum oxide as a base element like corundum, it has a high volume of beryllium mixed into it. Brilliant in appearance, chrysoberyls often occur in a yellow to green hue, although their lineament is best known for having a tendency to change color quite a bit under different types of lighting... middle of paper...not found in areas of hilly geographical instability such as earthquakes and volcanic. The basic chemical complement is made up of very common elements found deep in the earth's crust. What makes it expensive as a gemstone is the same factor that makes a diamond much more valuable than a lump of coal which would normally contain the same elements as the diamond. That is, with enough pressure and heat fusion of tectonic elements is applied to create a red gemstone well known as feldspar. Organic Gemstones: The best-known examples of this are amber and pearls. Mainly, organic gemstones are those that come naturally from organic sources rather than mineral sources. Oysters are a pearl, amber is a yellow formed from a fossilized tree. Although these are not gemstones per se, of course gemstones are still used extensively in jewelry, so they are included in this specification.