It never ceases to amaze me how detailed and varied gemstone classifications can be. Gemstones belong in several different classes, depending on their crystalline structure, their chemical composition, and the impurities present in each stone. To the majority of people, none of this matters, but to gemologists who have the privilege to work with and look at gemstones all day long, there are tons of ways in which to categorize these stones.
Precious vs. Semi-Precious
Gemstones can be classified in two different major groups. Precious and semi-precious gemstones are the most basic classes of jewelry-grade stones. There are fewer precious gemstones than semi-precious ones. Precious stones have the finest color, are translucent, and are usually more rare. Precious gemstones include diamond, ruby, sapphire and emerald. All other gemstones, including amethyst, peridot, and garnet, are semi-precious.
Minerals vs. Non-Mineral Gemstones
Some gemstones are considered minerals, while others are non-mineral. Minerals are made of things that have never been alive and consist of crystals. Corundum, for instance, is made up of oxygen and aluminum. Examples of corundum are sapphires and rubies. Another example would be diamond, which is made from crystals of one element, carbon.
Non-mineral gemstones are made from natural substances that have formed into beautiful gemstones due to natural processes. Some examples of non-mineral gemstones include pearl, coral, amber, and ammolite.
Natural vs. Synthetic Gemstones
Some gemstones are found in nature, while others, while still quite beautiful, have been man-made in a lab. The reasoning behind this has to do with cost of the gemstone and its rarity. Synthetic gemstones can have properties that are very similar to their natural counterparts. A stone found in nature after being formed deep in the earth for millions of years is a lot more rare, so it will cost a lot more than a stone made in a lab.
Most of the popular gemstones can be found in nature and in synthetic forms. For instance, ruby can be breathtakingly beautiful when it's found in nature and polished to accentuate its beauty. One particular stone may have inclusions or small cracks in the body of the stone that differentiate it from other stones similar in size and shape. A synthetic ruby, created in a lab, will have fewer distinguishing qualities and may even look more perfect. Commonly, a natural ruby may not be entirely translucent, while a synthetic ruby usually is.
The basic gemstone families include beryl, corundum, opal, quartz, spodumene, and zoisite. Within these groups, there can be more than one variety. Sometimes, one family of stones will contain types that have different names based on their color or some other difference that can be seen with the naked eye. Within the beryl family, for instance, are aquamarine and emerald, which are made of the same substance but are different colors. Quartz can be found in several different colors, including yellow, purple, blue, and green. Some types of quartz include amethyst and citrine. An example of zoisite is tanzanite.