Guide to Amethyst

Amethyst is the violet to purple variety of quartz. It is often associated with albite and orthoclase in pegmatites. Fine specimens of amethyst can be classified as semiprecious gemstones.

Fig. 1. Author Steven Marquez is seen working on the curation and cataloguing of the mineral collection at the Cripple Creek District Museum. Photo by Steven Veatch.

This specimen was found in Cripple Creek Colorado, as a near surface deposit on the David Leighton gold mine, owned by Steven Wade Veatch across from the hardware and grocery store on Teller County 1. The short, stubby amethyst crystals formed gas pockets in a hot, welded ash deposit that once covered the landscape of Cripple Creek. Amethyst is also mined in great quantities from the state of Minas Gerais in Brazil. A deep purple amethyst is commonly found in Uruguay.

The colour purple is a royal colour, which is why amethyst is often used in jewellery for kings and queens. It was highly valued by Egyptians and the ancient Greeks believed that it protected against intoxication. Amethyst is the birthstone for February.

Fig. 2. Note the faint crosswise striations on the surface of the amethyst crystal. This is one of the diagnostic features of quartz. The specimen is from the Steven Veatch collection. Photo by Steven Marquez.

Facts on file

Chemical formula: SiO₂
Composition: silicon dioxide; the colour is caused by iron or manganese impurities
Colour: purple, greasy lustre
Streak: white
Hardness: 7
Crystal system: hexagonal
Transparency: transparent to translucent
Specific gravity: 2.65
Lustre: vitreous
Cleavage: none
Fracture: conchoidal
Tenacity: brittle
Group: silicates, tectosilicates

Haiku

Brilliant purple

Never ceasing to amaze

Glowing like the stars

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Filed under: minerals Tagged: Amethyst, Cripple Creek, Crystals
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