Категория: ГеографияГеография

Native element. Minerals, sulfides, halides





Gold (Au) has golden yellow color, low hardness, high density (15-19 g/cm3),
chemical resistance, lack of oxidation products.
Origin and paragenesis. For gold, the most typical is an hydrothermal origin in
quartz veins. Gold is associated with arsenopyrite, pyrite, chalcopyrite, galena,
sphalerite, fahl ore. Gold accumulates in placers thanks to the chemical resistance in
association with quartz, magnetite, cassiterite, platinum. It is known metamorphic
sandstones with gold, chalcopyrite, pyrrhotite, pyrite, and chlorite.
Practical importance. Monetary metal. Gold is widely used in the jewelry business,
medicine, some instruments and reagents. World productionis about 1000 tons per
year. Gold content must be at least 4-5 g/t for primary deposit and not less than 0.1 g
/t for the placer accumulation.


Silver (Ag) has silver-white color on a fresh surface, gradually
become dim, covered with a skim of silver sulphide of black color,
malleable, high density (10-11 g/cm3).
Origin and paragenesis. Hydrothermal in association with pyrite,
galena, fahl ore, quartz, barite, calcite. Perhaps the formation of
hypergene native silver from the decomposition of sulfurous compounds
of silver in the oxidation zone of sulfide deposits.
Practical importance. Silver is used in the jewelry business, coinage, as well as in
various alloys, in photography, electronics.


Platinum (Pt) has high density (15-19 g/cm3), gray color, anti-acid,
resistant to the weathering, the melting point is 17710С.
Origin and paragenesis. Magmatic in connection with the basic
and ultrabasic rocks in association with olivine, pyroxene, chromite,
sulphides (pyrrhotite, chalcopyrite, pentlandite).
Practical importance. Monetary metal, it is used in jewelry, as well as for the production of
chemical resistant, acid- resistant ware, electrical engineering and medicine.


Native minerals of non-metals group
Diamond (C) has varieties: Bort - very small light-colored intergrowths
and aggregates unsuitable for faceting. Ballas - ball shaped bort, rounded
very small aggregates radially fibrous structure. Carbonado - porous
intergrowths of black color with lots of graphite inclusions and others
minerals, dense and with no visible cleavage. Unit of measurement of the
diamond is carat (1 carat - 0.2 g). A diamond is determined by the high hardness (10),
a strong adamantine luster, high refringence and shape of the crystals (Figure 1).
Origin and paragenesis. Magmatic in connection with the ultrabasic rocks in
kimberlites. Association with pyrope, ilmenite, olivine, phlogopite, serpentine and
magnetite. It is known in meteorites. Diamond is in the under surface conditions is
steady and accumulates in placer deposits.
Practical importance. Precious stone of the first class. It is used as an abrasive and
polishing material. Faceted diamond - polished diamond.


Graphite (C) - anthracitous amorphous form of carbon is
shungite. Graphite is easily recognized by the shape of the crystals
(Figure 1), black color, low hardness (1), eminent cleavage. It writes on
the paper, hands get dirty, greasy to the touch.
Origin and paragenesis. Magmatic, pneumatolytic (quartz and
pegmatite veins) and metamorphic (crystalline schists, gneisses, crystalline
limestones). Accessory mineral of meteorites. Association - quartz, feldspar, muscovite,
coal, bitumens, etc.
Practical importance. For manufacturing of pencils, as a lubricating material in
electrotechnical and rubber industry, in atomic industry.


Native sulfur (S) is easily determined by a bright yellow color, the
shape of the crystals (Figure 2), adamantine luster on the faces and
Origin and paragenesis. 1 - volcanogenic sulfur occurs in association
with realgar, orpiment, hematite, gypsum and zeolites; 2 - biogenic-sedimentary
sulfur in association with gypsum, anhydrite, celestite, aragonite, calcite; 3 - in the
oxidation zone of sulfide deposits.
Practical importance. For the production of sulfuric acid, sulfate cellulose, chemical
pesticides for agricultural pests.



Galena (PbS) has isometric grains, perfect cleavage on the cube, low
hardness (2.5), a significant density (7.5 g/cm ).
Origin and paragenesis. 1. Hydrothermal. Association with sphalerite,
sulphides of copper and silver in polymetallic ores. It is also found in
association with pyrite, pyrrhotite, barite, quartz and calcite; 2. Skarn. 3.
Sedimentary. It forms disseminations, mainly in bituminous carbonate rocks. In the oxidation
zone galena unstable and easily decomposed with the formation of the carbonate and sulfate of
lead and other minerals.
Practical importance. The most important lead ore. Silver, bismuth, sometimes
selenium are extracted in passing.


Sphalerite (ZnS) - varieties: marmatite black ferruginous, cleiophane - colorless or light
yellow, reddish. Isometric forms (Figure 3),
perfect cleavage, adamantine luster, trait- from
colorless to brownish.
Origin and paragenesis. 1. Hydrothermal. It is associated with galena, pyrite,
chalcopyrite and other minerals. 2. It is known volcanogenic and the sedimentary. In the
oxidation zone is easily destroyed with the formation of secondary minerals of zinc
(smithsonite and calamine).
Practical importance. Main zinc ore. Cadmium, indium, gallium, germanium, and
many other elements are extracted in passing.


Pyrite (FeS2) differs from chalcopyrite and pyrrhotite cubic
crystal form (Figure 5), high hardness (6-6.5), light -yellow color,
marcasite similar to it, but it has a characteristic shape.
Origin and paragenesis. Hydrothermal pyrite deposits. Association
- galena, sphalerite, chalcopyrite, fahl ore, arsenopyrite, gold,
quartz, calcite and others. It is known igneous, sedimentary and metamorphic
pyrite. It is easily oxidized in the surface conditions with formation of sulfates and
hydroxides of iron.
Practical importance. The basic raw materials for the production of sulfuric
acid. Sometimes nickel and cobalt are extracted from pyrite.


Chalcopyrite (CuFeS2) differs from pyrite lower hardness
and darker brass-yellow color, crystal forms (Figure 7), often
with blue or variegated tarnish. Unlike pentlandite has no
cleavage and a little bit lighter color.
Origin and paragenesis. 1. Magmatic in connection with the basic rocks in
association with pentlandite and pyrrhotite. 2. Skarn in association with andradite,
magnetite, sphalerite, and other minerals. 3. Metamorphic - cupreous sandstones
and shales. It is easily oxidized in the surface conditions with the formation of iron
hydroxides and various secondary copper minerals (malachite, azurite and others.).
In the zone of cementation thanks to chalcopyrite occurs bornite and chalcocite.
Practical importance. The most important copper ore. Sometimes silver, indium
and other metals are extracted in passing.


Bornite (Cu5FeS4) is determined by bronze-red color on a
fresh fracture and bright variegated tarnishing.
Origin and paragenesis. Hydrothermal in association with
chalcopyrite, pyrite, galena, sphalerite and fahl ore. In the
secondary enrichment zone of copper ores in association with
chalcocite and covellite. It is easily replaced in the surface conditions by secondary
copper minerals (malachite, azurite, and others).
Practical importance. Copper ore.



Fluorite (fluorspar) CaF2 - rare colorless, basically it is
painted in different colors: yellow, green, blue, purple,
sometimes purple-black. Determined by the habit of the cubic
crystals (Figure 14), perfect cleavage by the octahedron, low
hardness (h. 4), polychrome coloration.
Origin and paragenesis. Hydrothermal with quartz, barite, calcite and
sulfides; as well as quartz, chalcedony, cinnabar and stibnite. In greisens with
quartz, beryl, tourmaline, cassiterite, wolframite and topaz. Less common in skarns
with garnet and calcite.
Practical importance. Used in metallurgy as a flux in the smelting of aluminum.
Transparent colorless varieties of fluorite are used in optics. It is a source of various
fluorine compounds.


Practical importance. Galit - raw materials for the chemical and food industry
goes to produce HCl, soda, chlorine, NaOH.
Halite (rock salt) NaCl - colorless or white, is determined
by the readily soluble in water, the cubic crystals, perfect
cleavage by the cube, low hardness (h. 2), salty taste.
Origin and paragenesis. Chemical sediments of marine and
lake origin. In association with sylvite, gypsum, dolomite,
anhydrite, and other salts.
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