Quartz

Appearance, Uses and History

Locales

Quartz is found worldwide, and is one of the most common minerals on the Earth.

Listing locales would be difficult, there are excellent Quartz specimens on nearly every continent – many of the fine gemmy specimens available online are a few key locations, though.

• Minas Gerais, Brazil.
• Herkimer County, New York, USA
• Montgomery County, Arkansas, USA
• Madan ore field, Smolyan province, Bulgaria
• Hunan province, China
• Guangdong province, China
• Marrakesh-Safi, Morocco
• Western Sahara geode beds, Morocco
• Amoron’i Mania, Madagascar
• Zomba, Southern Malawi
• Agadez, Niger
• Chihuahua, Mexico
• Ancash, Peru
• Balochistan, Pakistan
• Gilgit-Baltistan, Pakistan
• Maramures, Romania
• Primorsky Krai, Russia
• Morogoro, Tanzania
• Cumbria, UK
• Cornwall, UK
• Artigas, Uruguay

Variations

There are numerous ‘sub-groups’ under Quartz, and it does get a little complicated.

The most important distinction to make is the difference between macrocrystalline and microcrystalline (also called cryptocrystalline). Microcrystalline varieties have individual crystals that are visible to the naked eye; microcrystalline varieties are aggregates of crystals only visible under high magnification.

There are various forms of both macrocrystalline and microcrystalline Quartz. Macrocrystalline varieties include rock crystal Quartz, Rose Quartz, Rutilated Quartz, etc, and microcrystalline varieties include Chalcedony, Carnelian, Aventurine, Agate, Onyx, Jasper, and Tigers Eye.

Common varieties of Quartz

Of Quartz itself, there are many well known varieties; going into specifics would take hours.

• Amethyst – a purple variety of Quartz ranging from a vivid violet purple to a pale lavender grey.
• Ametrine – a trade name given to a form of Amethyst with iron-stained or ferruginous quartz creating a mixture of purple and orange quartz in a single stone.
• Aura Quartz – a form of Quartz that has been metal film coated with precious metals to give it an iridescent sheen.
• Blue Quartz – a trade name given to included Quartz which has so many blue inclusions (dumortierite, riebeckite, etc) that it appears blue overall.
• Cactus Quartz – a trade name given to quartz with two generations of growth – one large crystal with many smaller crystals growing over it.
• Chlorite Quartz  – Quartz with inclusions of the mineral Chlorite – sometimes very transparent and prized as a gemstone.
• Citrine – a form of yellow to yellow-orange quartz.
• Dumortierite Quartz – Quartz with inclusions of dumortierite.
• Enhydro Quartz – quartz crystals with a liquid inclusion – typically, these are two phase inclusions (liquid and gas), because a liquid inclusion without a bubble or solid in is rarely spotted!
• Faden Quartz – quartz which has formed with a white line/thread like growth through the centre.
• Ferruginous Quartz – the technical term for quartz with iron staining and iron inclusions.
• Herkimer Diamond – a trade name for dual terminated Quartz crystals found in Herkimer, New York.
• Lemon Quartz – a trade name given to a form of yellow coloured quartz.
• Milky Quartz – sometimes known as snowy Quartz, a milky white form of Quartz caused by tiny inclusions trapped during the formation of the crystal. Often sold tumbled, found in large rough chunks.
• Morion – an alternate name for smoky Quartz, originally named Mormorion by Pliny the Elder.
• Phantom Quartz – a ‘phantom’ is an overlapping layer of crystal growths which is visible inside a crystal – possibly where one layer of growth formed with slightly more iron oxide, or chlorite, etc.
• Prase – a form of quartz given to varieties with green inclusions causing an overall green colouration to the piece.
• Prasiolite – a form of green Quartz, often artificially created by heating or irradiating amethyst. Some pieces are natural, however.
• Rock crystal Quartz – a form of clear, gemmy quartz.
• Rose Quartz – a pale pink to rosy pink-red hue. In some cases it may show asterism. Very popular for jewellery.
• Rutilated Quartz – clear Quartz with needle like inclusions of Rutile.
• Scepter Quartz – a larger quartz point which has grown atop a smaller quartz point, essentially forming a rod with a thicker quartz point to one end.
• Smoky Quartz – a grey-brown translucent to transparent form of Quartz, with a colour caused by irradiation.
• Star Quartz – a trade name for any Quartz showing asterism, a star on its surface.
• Tourmalinated Quartz – Quartz with Tourmaline inclusions, in the form of needle like straight crystals, typically black but sometimes pink, green, blue and other colours common to Tourmaline.

Mineralogy

Hazards and Warnings

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis.

Quartz especially has been linked to silicosis.

When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

Translations

Further Reading / External Links

• https://en.wikipedia.org/wiki/Quartz
• https://geology.com/minerals/quartz.shtml
• https://www.minerals.net/mineral/quartz.aspx
• https://www.mindat.org/min-3337.html