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2. Quartz - Wikipedia

   en.wikipedia.org/wiki/Quartz

   Because natural quartz is often twinned, synthetic quartz is produced for use in industry. Large, flawless, single crystals are synthesized in an autoclave via the hydrothermal process. [71] [22] [72] Like other crystals, quartz may be coated with metal vapors to give it an attractive sheen. [73] [74]

3. Cave of the Crystals - Wikipedia

   en.wikipedia.org/wiki/Cave_of_the_Crystals

   Cave of the Crystals or Giant Crystal Cave (Spanish: Cueva de los cristales) is a cave connected to the Naica Mine at a depth of 300 metres (980 ft), in Naica, Chihuahua, Mexico. It takes the form of a chamber within the limestone host rock of the mine, and is about 109 metres (358 ft) long with a volume of 5,000 to 6,000 cubic metres (180,000 ...

4. Prasiolite - Wikipedia

   en.wikipedia.org/wiki/Prasiolite

   Prasiolite (also known as green quartz, green amethyst or vermarine) is a green variety of quartz. Since 1950, almost all natural prasiolite has come from a small Brazilian mine, [citation needed] but it has also been mined in the Lower Silesia region of Poland. Naturally occurring prasiolite has also been found in the Thunder Bay area of Canada.

5. Herkimer diamond - Wikipedia

   en.wikipedia.org/wiki/Herkimer_diamond

   Herkimer diamonds are double-terminated quartz crystals discovered within exposed outcrops of dolomite in and around Herkimer County, New York, and the Mohawk River Valley in the US. [1][2] They are not diamonds; the "diamond" in their name is due to both their clarity and well formed faces. Because the first discovery sites were in the village ...

6. Amethyst - Wikipedia

   en.wikipedia.org/wiki/Amethyst

   Amethyst is a purple variety of quartz (SiO. 2) and owes its violet color to irradiation, impurities of iron (Fe3+. ) and in some cases other transition metals, and the presence of other trace elements, which result in complex crystal lattice substitutions. [2][3][4] The irradiation causes the iron Fe3+.

7. Pegmatite - Wikipedia

   en.wikipedia.org/wiki/Pegmatite

   Pegmatite. A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than 1 cm (0.4 in) and sometimes greater than 1 meter (3 ft). Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic composition to granite.