Quartz is the most common mineral on earth, making up about 12% of the Earth’s crust. Second only to feldspar, which is more common. However, one shouldn’t judge from this that quartz is uninteresting. In fact, the quartz family is surprisingly very diverse. The fact that they are inexpensive just means there are more opportunities for collectors.
All quartz is made of silicon dioxide, but this was not discovered until the early 19th century. Prior to that, various forms of quartz were thought to be distinct minerals. This is not actually surprising, since there are two different branches of the quartz family.
Macrocrystalline Quartz: When most people think of Quartz, they think of what is known as macrocrystalline quartz, which includes stone like: rock crystal, amethyst, aventurine, citrine, smoky quartz, rose quartz, blue quartz, hawk’s eye, Prasiolite, quartz cat’s eye, and tiger’s eye.
Macrocrystalline quartz, as the name suggests, has large crystals with distinct shapes that can be distinguished by the naked eye, that run the gamut from tiny druzies all the way up to crystals larger. These types of quartz are mainly transparent to translucent, with a vitreous luster.
Microcrystalline Or Cryptocrystalline Quartz: The other type of quartz is known as microcrystalline quartz. It has microscopically small crystals that are so minuscule and packed so tightly together that they’re completely indistinguishable to the naked eye. This type of quartz is usually translucent to opaque, with a waxy to dull or greasy luster. This kind of quartz is further divided into two subcategories, fibrous and granular.
The fibrous varieties of quartz are known as chalcedony, but this name covers a remarkable array of stones. In fact, the name chalcedony refers to solid colored microcrystalline quartz, especially of a light color. The patterned varieties of quartz tend to have their own names. The most prominent of these include agate, distinguished by its bands of color; onyx, which is black and white layered chalcedony; chrysoprase, an apple-green variety of chalcedony, colored by nickel. and carnelian, a yellow-orange to a reddish-orange variety that is colored by iron