Quartz is a chemical compound consisting of one part silicon and two parts oxygen. It is the most abundant mineral and widely distributed mineral found at Earth's surface, and its unique properties make it one of the most useful natural substances.
It is present and plentiful in all parts of the world. It forms at all temperatures. It is abundant in igneous, metamorphic, and sedimentary rocks. It is highly resistant to both mechanical and chemical weathering. This durability makes it the dominant mineral of mountaintops and the primary constituent of beach, river, and desert sand. Quartz is ubiquitous, plentiful, and durable.
Minable deposits are found throughout the world.
Quartz is also the most varied of all minerals, occurring in all different forms, habits, and colors. There are more variety of names given to Quartz than any other mineral.
Chalcedony is, in reality, a variety of quartz. Other important varieties of quartz are amethyst, ametrine, citrine, carnelian, aventurine, prasiolite, and agate.
The word "quartz" comes from the German quartz, which is of Slavic origin (Czech miners called it křemen). Other sources attribute the word's origin to the Saxon word Querkluftertz, meaning cross-vein ore. The Ancient Greeks referred to quartz as “κρύσταλλος” (krustallos) derived from the Ancient Greek word “κρύος” (kruos) meaning "icy cold" because some philosophers (including Theophrastus) believed the mineral to be a form of supercooled ice. Roman naturalist, Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time. Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz.
In the 17th century, Nicolas Steno's study of quartz paved the way for modern crystallography. He discovered that regardless of a quartz crystal's size or shape, its long prism faces always joined at a perfect 60° angle.
There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia.
Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties.
Quartz is extracted from open-pit mines. Miners only use explosives on rare occasions when they need to expose a deep seam of quartz. The reason for this is that although quartz is known for its hardness, it damages easily if it is suddenly exposed to a change in temperature, such as that caused by a blast.
Rutilated and tourmalinated quartz
Rutilated Quartz is usually clear or smoky quartz, or rarely citrine, which contains acicular, hair, or needle-like inclusions of rutile, an ore of titanium. These inclusions usually form as fine strands or fibers of metallic gold, silver, red, or brown. Gold is the most common, and its fine, flowing strands give rise to the alternative names Angel Hair Quartz and Venus Hair Stone. Rutile also occurs microscopically in rose quartz, its alignment refracting light to form an asterism or six-pointed star, which is sometimes referred to as 'starstone' or 'fairy star'. Rutilated quartz can be found in Brazil, Luxembourg, USA, and Belgium.
Tourmalinated Quartz is clear rock crystal (crystal quartz) which has grown together with black tourmaline, and shows strands of the tourmaline running through the quartz, hence "tourmalinated." The earliest use of tourmalinated quartz was for tools made by hominids in Ethiopia over 2 million years ago. Although it can be found in many parts of the world, tourmalinated quartz used for jewelry-making comes mostly from Brazil.
The difference between the two stones is that rutilated quartz is quartz with crystals of rutile, tourmalinated quartz is quartz with crystals of tourmaline.