The thin (1–three cm extensive) brighter layers are quartz veins, fashioned during the late stages of crystallization of granitic magmas. Like different crystals, quartz could also be coated with steel vapors to provide it an attractive sheen. Because natural quartz is usually twinned, artificial quartz is produced for use in business. Large, flawless, single crystals are synthesized in an autoclave through the hydrothermal process; emeralds are also synthesized on this trend.

It ranges in readability from almost complete transparency to a brownish-gray crystal that is almost opaque. The translucency outcomes from natural irradiation creating free silicon within the crystal. Amethyst is a type of quartz that ranges from a bright vivid violet to dark or boring lavender shade. The world's largest deposits of amethysts could be found in Brazil, Mexico, Uruguay, Russia, France, Namibia and Morocco.

Sometimes amethyst and citrine are discovered rising in the identical crystal. An amethyst is shaped when there's iron within the area where it was formed. 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.

Well-shaped crystals usually kind in a 'bed' that has unconstrained progress right into a void; usually the crystals are hooked up on the different end to a matrix and just one termination pyramid is current. However, doubly terminated crystals do occur the place they develop freely with out attachment, as an example within gypsum. A quartz geode is such a situation the place the void is approximately spherical in shape, lined with a bed of crystals pointing inward.

Color is a secondary identifier for the cryptocrystalline minerals, though it is a main identifier for the macrocrystalline varieties. The ideal crystal form is a six-sided prism terminating with six-sided pyramids at each end.

The Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος that means 'icy chilly', because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the term rock crystal is sometimes used instead name for the purest form of quartz.