Amethyst (or silica) occurs in various colours in nature, from pure transparent to almost opaque, from a pale lilac-reddish colour to a dark or light lilac. However, amethyst powder is white. It is both piezo- and piroelectric due to its crystal structure. It lets in UV light rays, and its symmetric structures also allow circular polarity. It is constituted by hexagonal columns, and often appears in the form of twin crystals. Amethyst cannot be cut; the breaking surface has a shell form.
It occurs mainly in so-called amethyst breccias and veins and various rock veins. Most frequent occurences are in: Brazil, Siberia, Uruguay, Canada, Zambia and Madagascar. In Hungary, the most frequent occurrences are in the vicinity of Telkibánya and the region of Gyöngyösoroszi.
One of its major characteristics is that amethyst loses its violet shade and gets discoloured when exposed to direct sun rays. However, it is the most favourable mineral among quartzes. It grows on the inner surface of agate, and it is usually several centimetres in size. Due to its particular colour, amethyst was a dominant shade in royal jewels since lilac symbolizes success, wealth and prosperity.
Citrine (or silica) occurs in the form of hexagonal columns, mainly as twin crystals, in their natural form. They cannot be split, and the breaking surface has a shell form. Its powder is white, and as a crystal it is also quite light or golden yellowish. It is always slightly clear. Just like amethyst, it has a symmetric structure, therefore is piezo- and piroelectric, and also lets in UV light rays.
On our continent, it mainly occurs in Spain, but Brazil and Scotland, or India and Russia are also rich in it.
Citrine occurs in a very wide range of yellow shades. It is a quite rare mineral and therefore is of high value.
Rock-crystal (also a silica) occurs in the form of hexagonal columns, mainly as twin crystals, in nature. They cannot be split, and the breaking surface has a shell form. Though its powder is white, as a crystal it is colourless in fact. Just like amethyst, it has a symmetric structure, therefore is piezo- and piroelectric, and also lets in UV light rays.
On our continent, it mainly occurs in the Alps, but Brazil, Madagascar and India are also rich in it.
Bohemian ruby (also silica) occurs in the form of hexagonal columns, mainly as twin crystals, in their natural form. They cannot be split, and the breaking surface has a shell form. Though its powder is white, as a crystal it can be quite light and pink. It is always slightly clear. Just like amethyst, it has a symmetric structure, therefore is piezo- and piroelectric, and let also UV light rays.
On our continent, it mainly occurs in the Ural mountains, but Brazil, Madagascar, the U.S. and South Africa, or Spain and Scotland are also rich in it.
Smoky quartz (also silica) occurs in the form of hexagonal columns, mainly as twin crystals, in nature. They cannot be split, and the breaking surface has a shell form. Though its powder is white, as a crystal it is yellowish-brown, smoky grey or even black. It is always slightly clear. Just like amethyst, it has a symmetric structure, therefore is piezo- and piroelectric, and also lets in UV light rays.
On our continent, it mainly occurs in the Alps, but Brazil, North America, Spain and Scotland are also rich in it. In Hungary, it occurs mainly around Telkibánya and Selmecbánya.