The
Merensky Reef, is a layer of
igneous rockIgneous rock is one of the three main rock types . Igneous rock is formed by magma being cooled and becoming solid. They may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks...
in the
Bushveld Igneous ComplexThe Bushveld Igneous Complex is a large layered igneous intrusion within the Earth's crust which has been tilted and eroded and now outcrops around what appears to be the edge of a great geological basin. Located in South Africa, the BIC contains some of the richest ore deposits on Earth...
(BIC) in the
TransvaalThe Transvaal is the name of an area of northern South Africa. Originally the bulk of the independent Boer South African Republic, after the Anglo-Boer War of 1899-1902 it became the Transvaal Colony, and one of the founding provinces of the Union of South Africa, with its regional capital in...
which together with an underlying layer, the Upper Group 2 Reef (UG2), contains most of the world's known reserves of
platinum groupThe platinum group metals sometimes collectively refers to six metallic elements clustered together in the periodic table....
metals (PGMs) or platinum group
elementsA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
(PGEs) -
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements...
,
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
,
rhodiumRhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45...
,
rutheniumRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
,
iridiumIridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
and
osmiumOsmium is a chemical element that has the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is the densest natural element. The density of osmium is , slightly greater than that of iridium, the second densest element....
.
The UG2 Reef, the composition of which is relatively consistent throughout the BIC, is rich in
chromiteChromite is iron magnesium chromium oxide: Cr
2O
4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts; also, aluminium and ferric iron commonly substitute for chromium....
, but lacks the Merensky's
goldGold is a chemical element with the symbol Au and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is...
,
copperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
and
nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
by-products, though its PGM reserves may be almost twice those of the Merensky Reef.
ChromititeChromitite is an igneous cumulate rock composed mostly of the mineral chromite. It is found in layered intrusions such as the Bushveld Igneous Complex in South Africa and the Stillwater igneous complex in Montana.-References:...
layers occur commonly in large
maficMafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term was derived by contracting "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
layered intrusions.
The
Merensky Reef, is a layer of
igneous rockIgneous rock is one of the three main rock types . Igneous rock is formed by magma being cooled and becoming solid. They may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks...
in the
Bushveld Igneous ComplexThe Bushveld Igneous Complex is a large layered igneous intrusion within the Earth's crust which has been tilted and eroded and now outcrops around what appears to be the edge of a great geological basin. Located in South Africa, the BIC contains some of the richest ore deposits on Earth...
(BIC) in the
TransvaalThe Transvaal is the name of an area of northern South Africa. Originally the bulk of the independent Boer South African Republic, after the Anglo-Boer War of 1899-1902 it became the Transvaal Colony, and one of the founding provinces of the Union of South Africa, with its regional capital in...
which together with an underlying layer, the Upper Group 2 Reef (UG2), contains most of the world's known reserves of
platinum groupThe platinum group metals sometimes collectively refers to six metallic elements clustered together in the periodic table....
metals (PGMs) or platinum group
elementsA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
(PGEs) -
platinumPlatinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is in Group 10 of the periodic table of elements...
,
palladiumPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
,
rhodiumRhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45...
,
rutheniumRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
,
iridiumIridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
and
osmiumOsmium is a chemical element that has the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is the densest natural element. The density of osmium is , slightly greater than that of iridium, the second densest element....
.
The UG2 Reef, the composition of which is relatively consistent throughout the BIC, is rich in
chromiteChromite is iron magnesium chromium oxide: Cr
2O
4. It is an oxide mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts; also, aluminium and ferric iron commonly substitute for chromium....
, but lacks the Merensky's
goldGold is a chemical element with the symbol Au and an atomic number of 79. It has been a highly sought-after precious metal for coinage, jewelry, and other arts since the beginning of recorded history. The metal occurs as nuggets or grains in rocks, in veins and in alluvial deposits. Gold is...
,
copperCopper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color...
and
nickelNickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature, other three being iron, cobalt and gadolinium...
by-products, though its PGM reserves may be almost twice those of the Merensky Reef.
ChromititeChromitite is an igneous cumulate rock composed mostly of the mineral chromite. It is found in layered intrusions such as the Bushveld Igneous Complex in South Africa and the Stillwater igneous complex in Montana.-References:...
layers occur commonly in large
maficMafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term was derived by contracting "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
layered intrusions. A current theory is that chromitites form as a result of introduction and mixing of chemically primitive
magmaMagma [from Greek μάγμα, paste] is molten rock that is found beneath the surface of the Earth, and may also exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and gas bubbles. Magma often collects in a magma chamber inside a volcano...
with a more evolved magma, which leads to supersaturation of chromite in the mixture, which in turn leads to the formation of a nearly monomineralic layer on the
magma chamberA magma chamber is a large underground pool of molten rock found beneath the surface of the Earth's crust. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
floor.
The initial recovery of platinum in South Africa took place on several of the large East Rand gold mines and the first separate platinum mine was a short lived venture near Naboomspruit that worked very patchy quartz reefs. The discovery of the Bushveld Igneous Complex deposits was made in 1924 by a Lydenburg district farmer, A F Lombaard. This was an alluvial deposit but its importance was recognised by
Hans MerenskyHans Merensky was a South African geologist, prospector, scientist, conservationist and philanthropist...
whose prospecting work discovered the primary source in the Bushveld Igneous Complex and traced it for several hundred kilometres by 1930. Extensive
miningMining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, vein or seam. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt and potash...
of the Reef did not take place until an upsurge in the demand for platinum group metals used in exhaust
pollutionPollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light...
control in the 1950s, made exploitation economically feasible. Extraction of metals from the UG2 chromitite could only take place in the 1970s with major advances in
metallurgyMetallurgy is a domain of materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. It is also the technology of metals: the way in which science is applied to their practical use...
.