Quartz

Quartz is one of the most important minerals on earth and makes up one of the most popular gemstone groups in the world of colored stones. It is the second most abundant mineral found in Earth's continental crust, second only to the feldspars. The name 'quartz' is thought to be derived from the German word 'quarz', which likely originated from the Slavic and Polish words meaning 'hard'. The name is descriptive in regard to quartz being the definitive mineral that measures 7 on the Mohs scale of hardness. Other gemstones are often compared to quartz when it comes to classifying them as being hard, soft or durable.

There are two main varieties of quartz, which can be further subdivided into other, more specific varietal names. All quartz gemstones share the same silicon dioxide (SiO2) chemical composition, but they have differing crystal classes and formations. The two main branches of quartz include macrocrystalline quartz and cryptocrystalline quartz. Macrocrystalline quartz includes amethyst, rock crystal, blue quartz, citrine, hawk's eye, prasiolite, quartz cat's eye, smoky quartz, rose quartz and tiger's eye. Macrocrystalline quartz is typically transparent to translucent and forms with larger crystals than cryptocrystalline quartz. Cryptocrystalline quartz forms with microscopically small crystals, which in most cases cannot be seen even under magnification. Cryptocrystalline quartz intergrown with moganite, a polymorph of quartz, is referred to as chalcedony. Chalcedony actually includes a wide variety of quartz gemstones, including agate, chrysoprase, bloodstone, jasper and carnelian. Chalcedony 'in the narrow sense' typically refers only to lighter and single-colored chalcedony, typically bluish in color. Cryptocrystalline quartz is usually opaque or translucent in clarity.

Quartz gemstones are very attractive, durable and hard. Also in most cases, quartz is fairly inexpensive and available in very large sizes. Some quartz varieties can be extremely rare, while others are very readily available. Quartz is an extremely versatile material that can be cut and carved into many shapes and sizes. It has been used for centuries in the creation of jewelry and ornamental objects. Today, quartz is not only one of the most important gemstones in the colored stone trade, but it also has many important industrial usages.