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Kathy Feick
Chromite is the main source of the metal chromium, a metal used to induce hardness, toughness and chemical resistance in steel. It was named after its chemical composition, chromium oxide. The mineral is brownish to black in colour with a dark brown streak. It has a conchoidal or an uneven fracture as well as no distinct cleavage. Crystals are small and rare. It may occur in octahedrons but it is most commonly found as a massive structure. Finally, although not all samples of chromite are magnetic some specimens may show slight magnetism.
Occurrences:
Chromite is a cumulate mineral which is found in ultramafic portions of layered mafic intrusions or in serpentines and other metamorphic rocks derived from the alteration of ultrabasic rocks. Due to its high crystallization temperature, this mineral is often found in the lower parts of magma bodies from the fractional crystallization process. It is commonly found in meteorites. Occurrences include:
- South Africa (the world’s largest chromite miner)
- United States (found in many locations, but only sparingly)
- Turkey
- Philippines
- Russia
- Canada
As well, since chromite is a very durable mineral, it also occurs in the sands of a few places.
Chrome mining in Canada (The Ring of Fire):
In April 2010 the Government of Ontario announced that they would be opening up a large chromite deposit to development in northern Ontario. The area that is to be mined is known as the “Ring of Fire”. It has an area of 5,120 square kilometres and is said to hold one of the richest ore deposits in the world. Minerals which are found in this deposit include copper, nickel, platinum, diamonds, palladium, gold, silver and of course chromite. This deposit of chromite is incredibly large. In fact, it is possible that there is enough chromite in this area for Canadian stainless steel for the next century! The Ring of Fire is arguable Ontario’s biggest mineral discovery in the last century.
The search for the Ring of Fire began with several junior exploration companies (Spider Resources Inc., KWG Resources Inc., and Freewest Resources Inc), which were digging for diamonds in northern Ontario. Even the much larger diamond companies De Beers Canada Inc began to re-examine the area for diamond producing kimberlite pipes. What they found instead were the presence of copper and zinc deposits. In 2007, Noront Resources Ltd found high-grade nickel with copper and palladium. This excited mine operators and talk about the Ring of Fire began. Noront and Freewest each discovered notable deposits of chromite as well. When U.S. iron ore and coal producer, Cliffs Natural Resources Inc heard of the promising area they purchased the company Freewest. By 2015 Cliffs expects to be producing 1 million to 2 million tonnes of high-grade chromite annually.
The price of success:
The Ring of Fire covers more than 40% of the province of Ontario but less than one percent of the provincial population lives in the area. There are a total of 24,000 First Nations people, in 36 communities, which inhabit the region. In addition, mining puts a stress on the environment and would likely damage the biodiversity and ecological integrity which may include habitat loss/ alteration, habitat fragmentation, introduction of foreign species and of course pollution and land degradation.
Uses:
- Used to harden steel, to manufacture stainless steel and to form alloys
- Used in plating to produce a hard, beautiful surface and to prevent corrosion
- Used to give glass an emerald green colour. it is responsible for the green colour of emeralds and the red colour of rubies
- Wide use as a catalyst
- Dichromites such as K2Cr2O7 are oxidizing agents and are used in quantitative analysis and also in tanning leather
- Lead chromate as chrome yellow is a pigment
- Compounds are used in the textile industry as mordants
- Used by the aircraft and other industries for anodising aluminum
- The refractory industry uses chromite for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stable crystalline structure
- Tanning leather
References:
Chromite-mineral properties and uses
Minerals Zone: http://www.mineralszone.com/minerals/chromite.html