9: Crystalline Quartzes

Iron can dye quartz yellow, in which case it is usually called citrine, or violet, making it amethyst. In contrast, aluminium colours quartz crystals dark brown or grey. These are called smoky quartzes.

Quartz is used in large quantities for different purposes, such as in the production of glass and ceramics. Quartz crystals can also be used in watches, sandpaper and sandblasting. Particularly beautiful quartz crystals are used in ornaments and jewellery. Quartz has been found all over the world. The largest crystals have weighed several tonnes. Quartz deposits in Finland include Kuopio and the Forssa region.

Smoky Quartz

The small quartz grains in granites are often smoky quartz. The very dark variety of smoky quartz is called Morion. A yellowish-brown type of smoky quartz can be found in Scotland, named Cairngorm after its place of discovery. In Finland, smoky quartz has been found in Lapland and at least in Viitaniemi, Orivesi.

Rose Quartz

Rose quartz comes from several places, including the United States, Namibia, Sweden and even several deposits in Finland. Our most famous deposit is probably in Muhos, Northern Ostrobothnia.

Amethyst

Until quite recently, amethyst was considered one of the cardinal gems, the most precious gemstones of all. Amethyst gems were used to decorate the clothing and regalia of kings and aristocrats, and common people could not afford them. Later, when extremely large amethyst deposits were found in Brazil, Uruguay and Southern Africa, the value of amethyst crashed, and it became accessible to people outside the upper class. Amethyst is mined all over the world, but the largest mines are in Brazil. Amethyst is mined substantially also in Zambia, Uruguay, the United States and Russia, and to a smaller extent, in Central Europe. Amethyst has also been found in the Finnish Lapland in several locations, the most famous one being the amethyst mine in Luosto.

Citrine

Citrine can also be produced artificially by heating amethyst to around 470–560 degrees Celsius. Depending on the origin, the amethyst colour can then turn pale yellow, almost orange, completely clear, i.e. colourless, or rarely, green, in which case it is called prasiolite. The majority of citrine on the market is now heat-treated amethyst.

Tiger’s Eye

Tiger’s eye was previously considered to be very rare and valuable, but due to large new deposits in South Africa and Australia, its price has decreased. Blue tiger’s eye is also known as hawk’s eye. Heat-treating (and sometimes natural processes) can turn tiger’s eye into a deep reddish-brown stone, known as bull’s eye.