Smoky Quartz

Group: Quartz Mineral class: Oxide Colour smoky grey, brown, black Colouring substance: radioactive substances, which change the crystal structure Pleochroism: medium: brown, brown-reddish Mohs’ hardness: 7 Density: 2.65 Cleavage: absent Fracture: conchoidal, very splintery Crystal system: trigonal, 6-faced prisms Transparency: transparent Lustre: wax lustre, vitreous lustre Fluorescence: usually none

Its characteristic brown colour is usually evenly distributed all over the gemstone. Apart from some Roman engraved pieces, there is almost no evidence of its utilisation in the antiquity.

Most of these stones lose their colour if they are heated up to 300-400C, although some of them turn yellow and become citrins. A particularity of Smoky Quartz is the abundant inclusions of liquids, garnets or rutile needles.

Predominantly in magmatic rivers. The most important deposits are in Brazil, Madagascar, Sri Lanka and Austria.

Very good for faceted cuts. Very often in emerald cut, baguette, oval cut and circular cut. If the inclusions of rutile needles are abundant, it can be cut as a cabochon or in form of beads.

It can be confused with andalusite or with tourmaline.