OCCURRENCE OF PRECIOUS STONES
Of the primary deposits of precious stones, pegmatite deposits are the most common. However, only some of them contain valuable gemstones. Such deposits are the pegmatites of the Urals, abundant in various stones. Discovery at the end of the 18th century. in the middle Urals, rare raspberry tourmalines in the vicinity of the village of Murzinka, as well as cherry red, pink, purple and green caused a great sensation among European mineralogists and gemologists. Two-color tourmalines enjoyed particular interest, of different shades, which were held in high esteem. Very beautiful topazes have also been found near Murzinka, distinguished by transparency and purity, with various shades of yellow, green and blue. Colorless and light blue topaz crystals, the weight of which sometimes reached several kilograms, found at the same time in the Ilmene Mountains in the South Urals, where the presence of beryllium has also been found, tourmalines, zirconias, pomegranates and amazonites.
At the end of the 18th century. The colorful beryls from the vicinity of Murzinka were also famous, among which were found rare beryls of pink color. In the river valleys of the middle Urals, mountain crystals and amethysts have long been mined; specimens containing acicular ingrowths of rutile and actinolite crystals were especially appreciated. The most sought-after and highly valued emeralds come from the Urals, chrysoberyl, fenakity i in.
Brazil's pegmatites are also very rich in precious stones, especially in the counties of Minas Gerais and Minas Novas, containing numerous beryls, topazy, tourmaline, amethysts, agates and others.
Numerous gemstones come from Madagascar's pegmatites, in which beryllium was found, tourmaline, topazy, spinele, kunzits, grenades, cordierites, amazonites and transparent golden feldspars.
The pegmatites in California deserve similar attention (Pala district, San Diego), where the beautiful craftsmen come from, pink beryls and similarly colored tourmalines.
South Asia has the most beautiful rubies, of sapphires and spinels are provided by metamorphized limestones found in Burma. In Ceylon, many different precious stones have long been mined from secondary alluvial deposits, which were originally associated with metamorphic rocks: gnejsami, slate and crystalline limestone. Similar alluvial deposits containing rubies, sapphires and zircons are found in Vietnam and Siam.
Rare deposits of emeralds are associated with metamorphic rocks. Colombia's emeralds are found in metamorphised limestones, rich deposits of emeralds are associated with biotite shale (okolice Swierdłowska) in the Urals, which is also rich in other gemstones.
The value of the world production of precious stones, assessed in the pre-war period, reached one percent share in the global mining production. Currently it is estimated at approx 0,5%, which does not mean a reduction in the world extraction of precious stones at all. It has to do with the growth of the world's population and the development of industry, what causes, that the percentage of the value of energy resources has recently exceeded 3/4, while the share of metallic raw materials in world production exceeded 1/5 the total value of mined minerals.