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MINERALS:

A mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific chemical composition. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms. The study of minerals is called mineralogy.

To be classified as a true mineral, a substance must be a solid and have a crystalline structure. A mineral is (generally) an inorganic, naturally occurring, organized crystalline structure composed of a single chemical compound or element. Mineral crystals form because their component chemicals tend to aggregate together in certain specific arrangements dictated by the shapes and components of the molecules involved (and sometimes varying with temperature and pressure). These arrangements result in the crystal forms described in the physical characteristics. Often, minerals are formed as a solution changes in some way which allows or forces the component mineral(s) to solidify. This change may be temperature, pressure, chemistry, or concentration, and the solution may be aqueous or a magma or even a gas.

PHYSICAL PROPERTIES:
Classifying minerals can range from simple to very difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming.

Physical properties commonly used are:
  1. Crystal structure and habit
  2. Hardness
  3. Luster
  4. Color
  5. Streak
  6. Fracture
  7. Cleavage
  8. Specific Gravity

CHEMICAL PROPERTIES:

Minerals may be classified according to chemical composition. They may be:

SILICATE CLASS
The largest group of minerals by far are the silicates (most rocks are ≥95% silicates), which are composed largely of silicon and oxygen, with the addition of ions such as aluminium, magnesium, iron, and calcium. Some important rock-forming silicates include Quartz, Mica, Feldspars etc.

CARBONATE CLASS
The carbonate minerals consist of those minerals containing the anion (CO3)2- and include calcite and aragonite (both calcium carbonate), dolomite (magnesium/calcium carbonate) and siderite (iron carbonate). Limestone, Marble, Talc etc are included in this class.

SULFATE CLASS
Sulfate minerals all contain the sulfate anion, SO42-. Sulfates also occur in hydrothermal vein systems as gangue minerals along with sulfide ore minerals. Common sulfates include Barite (barium sulfate), and gypsum (hydrated calcium sulfate) etc.

HALIDE CLASS
The halide minerals are the group of minerals forming the natural salts and include halite (sodium chloride), sylvite (potassium chloride). Halides, like sulfates, are commonly found in evaporitic settings where highly saline waters slowly evaporate, allowing the formation of both sulfates and halides at the water-sediment interface. The halide class includes the fluoride, chloride, bromide and iodide minerals.

OXIDE CLASS
Oxide minerals are extremely important in mining as they form many of the ores from which valuable metals can be extracted. They also carry the best record of changes in the Earth's magnetic field. They commonly occur as precipitates close to the Earth's surface, oxidation products of other minerals in the near surface weathering zone, and as accessory minerals in igneous rocks of the crust and mantle. Common oxides include hematite (iron oxide), magnetite (iron oxide), chromite (iron chromium oxide). The oxide class includes the oxide and the hydroxide minerals.

SULFIDE CLASS
Many sulfide minerals are economically important as metal ores. Common sulfides include pyrite (iron sulfide – commonly known as fools' gold), chalcopyrite (copper iron sulfide). The sulfide class also includes the selenide, the telluride, the arsenide, the antimonide, the bismuthinide, and the sulfosalt (sulfur and a second anion such as arsenic).

Minerals in Pakistan:

Pakistan covers more than 6,00,000 sq km area which demonstrates varied geological potential of metallic and non-metallic mineral deposits. Pakistan is very rich in non-metallic minerals. Major minerals of Pakistan are: Barite, Bentonite, Gypsum, Marble, Halite, Iron, Chromite, Coal, China Clay, Fire Clay etc.

Deposits in Pakistan:

Over 5 Million Tonnes of Barite are present and further discovery is being made.
Over 6 Million Tonnes of Bentonite is present and further exploration is being made.
Over 100 Million Tonnes of Halite is present.
Over 250 Million Tonnes of Mica is present.

BARITE:
It is Barium Sulfate. It is most commonly used in Oil-well drilling, manufacture of glass, paints, insecticides etc. In 1960’s its annual production was 10,000 tons, where as in 1974-1975 it was estimated 20,000 tons. In 1985-1986 it increased upto 42,000 Tons. By year 2000 it reached 125,000 tons. In 2007 it was approximately 450,000 and every year the production of Barite is increasing along with its exploration. The reserves of barite are increasing widely which are of high quality.

BENTONITE:
It is also known as Montmorilonite. Its annual production was 1,500 – 2,000 tons in 1995. Recently this has increased up to 200,000 Tons. It is used in Oil Industries, foundries, Steel Mill, sealing reservoir etc. The deposits are mainly in the Salt Range at Qadirpur and salt range at rohtas.

HALITE:
It is also known as Rock Salt. Its annual production in 1947-48 was 163,000 Tons. In 1984-85 It increased upto 573,000 tons. Large deposits are available in different areas of the country. It is available in Khewra, kalabagh, Warcha and Jatta. At Khewra the annual production is 220,000 tons. In warcha the production is approximately 80,000 Tons.