[Geography Notes] on Sulfide Minerals Pdf for Exam

Minerals that contain persulfide or sulfide as the major anion are sulfide minerals. What is Sulphide ? Compounds containing one or more sulphide ions are sulphides. Most of the sulfide minerals are economically important as metal ores. These are inorganic compounds. Sulfide minerals are structurally simple. They not only exhibit high symmetry in their crystal forms but also have many metallic characteristics, such as electric conductivity and metallic luster. Sulfide minerals have low hardness and higher specific gravity. Generally, sulfides are opaque, sectile, and have high density. Sulphide is more readily soluble in water and oxidizes the accompanying iron into double iron oxides. The chemical formula of sulphide  is S²⁻.

Types of Sulfides

Selenides, tellurides, arsenides, antimonides, bismuthinite, and sulfosalts are the major classes of sulphide ores. Sulfides are mostly opaque with different color variations and different streaks. The color of mineral powder obtained from sulfide minerals is known as the Streak. The non-opaque varieties have a high refractive index. Here are some common sulphide ores examples.

Bismuthinite

It is a name of sulphide ore. Bismuth is extracted from the Bismuthinite ore. Mostly found in complex mixtures of ores of gold, silver, etc and bismuth is extracted in form of a by-product. Their color varies from lead-grey to tin white, may have yellowish or varied tarnish. It is used in the pharmaceutical and chemical sectors and also as a fusible metal alloy.

Chalcopyrite

One of the most important minerals is copper (Cu). It has a metallic luster, greenish-black streaks, and is commonly tarnished in golden color. Chalcopyrite often occurs in crystals, they are usually found in massive chunks. The crystal is scalenohedral shaped. It is softer and yellower than pyrite. It is found in Japan, Spain, and South Australia, etc.

Galena – Lead Sulfide

 It has a dark grey streak and has a density that is about 7.5 times higher than water. It is very bright and lustrous. Mostly Galena is straight grey, very often it is found in bluish-grey color. Galena is formed in between low to medium temperature ore veins, along with sulfide and carbonate minerals. Silver is often found as an impurity and silver is also an important byproduct of the lead industry. It is used as a source of lead in ceramic glaze.

Marcasite

Same as pyrite but the crystal structure is different. It forms groups of cockscomb aggregates. Marcasite has lighter brass color than pyrite but its tarnishes are darker. The streaks of pyrites are greenish-black where the streaks of Marcasites are gray. They are unstable and often its decomposition creates sulphuric acids. Marcasite is used for powerful meditation, to heal the chakras. It is found in England, Dover and Derbyshire, Russia, France, Mexico, etc.

Pyrite 

Most common mineral Iron Sulfide. It is one of the most important sulfur-containing minerals. The Mohs hardness of Pyrite is around 6. It is brass-yellow with greenish-black streaks. It slightly resembles gold but pyrite is much lighter and harder than gold. Fool’s gold. formally known as pyrites In many places, Pyrites contain silver and gold as containment. Pyrites crystals are called pyritohedron. Pyrite is used in the paper industry and the manufacture of sulfuric acid.It is a sulphur ore .

Solved Examples

What is Fool’s Gold?

Fool’s gold is formally known as pyrites. Pyrites are usually brass-yellow and have a metallic luster. Due to which it gives a superficial resemblance to gold so it is termed as fools gold. The word pyrite is a greek derived word that means fire. Not only that Pyrites also contain gold as contamination. Pyrite also creates fire when struck with another rock. Pyrites are more brittle than gold and will break as it is not bendable like gold.

What is Molybdenite?

It is a metal sulphide. It is often confused with graphite. It is dark, very soft with a greasiness feel. Molybdenite forms hexagonal crystals like graphite. It is more metallic than graphite. Molybdenum in trace amounts is necessary for life because to fix nitrogen for building protein, an atom of molybdenum is required. It is also the primary source of molybdenum. 

 

Are Pyrites Toxic?

Pyrites are sulfide minerals. They are composed of sulfur and iron and act as one of the major contaminants of groundwater, lakes, and streams. Oxidation of Pyrite due to the burning of coal releases toxic metals like Arsenic. Miners are often affected with lung cancer due to this reason Lead is poisonous to humans as well as the environment. 

Conclusion

The symbol of sulphide is S²⁻ .Sulfide minerals are economically important. Sulfides can be toxic or not. It has metallic properties including electrical conductivity, refractive index, etc. There is a lot of variety in sulfide minerals. They also play an important role in pollution. Be it Air pollution, water pollution or soil pollution sulfide minerals play a major role. Smelting of iron ores and burning coal, which contain sulfur impurities causes air pollution. The breakdown of sulfides due to weathering at the earth’s surface releases toxic to both soil and water. But the fact cannot be denied that sulphide ores are common for metals like gold and silver as they are found in containment.