Quartz is one of the most well-known minerals on earth. It occurs in basically all mineral
environments, and is the important constituent of many
rocks.
Quartz is also the most varied of all minerals, occurring in all
different forms, habits, and colors. There are more variety names given
to Quartz than any other mineral. Although the
Feldspars as a group are more prevalent than Quartz, as an individual mineral Quartz is the most common mineral.
Most mineral reference guides list
Chalcedony as an individual mineral, but in reality it is a variety of Quartz. It is the
microcrystalline form of Quartz, forming only occurs in microscopic, compacted crystals. This page deals only with the
crystalline forms of Quartz.
Chalcedony is listed on its own dedicated page in this guide. Other important varieties of Quartz, such as
Amethyst,
Citrine, and
Agate, also have dedicated pages due to their popularity and individual varieties.
Some forms of Quartz, especially the gemstone forms, have their color enhanced. Almost all forms of the yellow-brown variety Citrine are in fact
heat treated. Much Amethyst is also heat treated to intensify color, and a green transparent form known as "Green Amethyst" or "Prasiolite" is formed by heat treating certain types of Amethyst. There is also a transparent sky blue form of Quartz crystals, as well as a wildly
iridescent type that are synthetically colored by
irradiation of gold. In some localities,
Hematite forms a thin red or brown layer internally in the Quartz crystal, giving it a natural bright red to brown coloring, and sometimes even a mild natural
iridescence.
Quartz frequently forms the inner lining of
geodes. Most geodes have an inner layer of larger
crystalline Quartz, and an outer layer of
Chalcedony or
banded Agate.
For additional information, see the gemstone section on Quartz. Hide
