Geology

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A

Agate Most agates occur as nodules in volcanic rocks or ancient lavas where they… Agglomerate The rock consists of 30% or more by volume of fragments in a clay-rich or… Albite Albite is most often associated with the plagioclase series feldspars where… Amethyst Amethyst is the purple variety of quartz. The name "amethyst" comes from the… Amphibole Gneiss This rock consists mainly of amphibole, feldspar and quartz. It is the… Amphibolite This rock consists mainly of amphibole, feldspar and quartz. It is the… Anorthite Anorthite is an end member and one of the rarer members of the plagioclase… Arsenopyite A major ore of arsenic, Arsenopyite can contain a small amount of gold as an…

B

Banded Iron Formation This rock consists of alternating thin layers of chert and iron minerals such… Barberton Supergroup The greenstones are economically important, hosting many gold, antimony,… Biotite Biotite is a common rock forming mineral, being present in at least some… Biotite Gneiss Mineralogically this gneiss consists mainly of feldspar and quartz with… Biotite Schist The rock consists chiefly of mica with subsidiary amounts of quartz and / or… Bornite Bornite is an important copper ore mineral. It ranks up there with many of… Breccia Consist of more than 30% angular fragments in a matrix (groundmass) of sand… Bushveld Igeneous Complex The Bushveld Igneous Complex (or BIC) is a large layered igneous intrusion…

C

Calcite Calcite, which gets its name from "chalix" the Greek word for lime, is a most… Calcrete The rock forms as primary deposits or through the replacement of existing… Cape Supergroup The Cape Supergroup consists of : All three groups intensively folded and… Chalcopyrite Chalcopyrite (or copper pyrite), looks like, and is easily confused with… Chert It is a dark coloured fine-grained silica rock that occurs as beds in… Coal Coal originates through the collection of plant material under anaerobic… Conglomerate Consist of more than 30% rounded fragments in a matrix (groundmass) of sand… Copper Native copper (copper found in a chemically uncombined state) has been mined…

D

Diamictite This rock consists of pebbles and angular fragments in poorly sorted matrix.… Diopside Diopside is an important rock forming mineral in several metamorphic and… Dolerite A fine to medium-crystalline rock consisting of plagioclase and pyroxene.… Dolerite Intrusions Summarised from Hydrogeology of the Main Karoo Basin: Current Knowledge and… Dolomite Dolomite, which is named for the French mineralogist Deodat de Dolomieu, is a… Dolomite In this case the rock consists for more than 90% of dolomite and less than… Drakensberg and Lebombo Group Taken from http://www.geology.ukzn.ac.za Dramatic outpourings of lava spread…

G

Galena Galena is a common mineral. Its characteristic cubes, distinctive cleavage… Geology Earth science including physical geology and geophysics; the history of the… Goethite Goethite has had a reputation for making rather uninteresting, dull and… Gold Gold is a very stubborn element when it comes to reacting to or combining… Granite A coarse crystalline rock consisting of quartz, potash feldspar, plagioclase,… Granite Gneiss Mineralogically a gneiss consists mainly of feldspar and quartz with variable… Graphite Graphite is a polymorph of the element carbon. diamond is another polymorph.… Gypsum Gypsum is one of the more common minerals in sedimentary environments. It is…

H

Hematite Hematite has several varieties, each with their own unique names. Hematite… Hornblende Hornblende is actually the name given to a series of minerals that are rather… Hypersthene Hypersthene is a relatively common mineral and is found in igneous and some…

J

Jasper Jasper is an opaque variety of Chalcedony occurring in all colours. It is…

K

Kaolinite Kaolinite, which is named for its type locality, Kao-Ling, Jianxi, China; is… Kimberlite This rock is fine-crystalline, non-equigranular to porphyritic and consists… Kimberlite Intrusions Taken from http://www.geology.ukzn.ac.za and Hydrogeology of the Main Karoo…

L

Lava A fine-crystalline rock consisting of plagioclase and pyroxene.Lava is molten… Limestone The rock consists for more than 90% of calcite and less than 10% dolomite.… Limonite Limonite is not a true mineral but a mixture of similar hydrated iron oxide… Limpopo Belt The 250 km wide Limpopo belt of southern Africa is an east-northeast trending…

M

Magnetite Magnetite is a natural magnet, hence the name, giving it a very nice… Malmesbury Supergroup and Cape Granite Suite (The Cape Granite Suite: A short introduction by Arnaud Villaros, 2006) The… Marble Marble forms as the result of the metamorphism of limestone and dolomite.… Meta-Conglomerate It is the result of medium to high grade metamorphism of a… Metamorphic Breccia It may form as the result of the metamorphism of a sedimentary breccia or due… Microcline Microcline is a common, but not a well known mineral and has been used as a… Minerals A mineral is a naturally occurring solid chemical substance that is formed… Montmorillonite Montmorillonite is a member of the general mineral group the clays. It… Mudstone This is a mixture of silt and clay, characterised by irregular fracture… Muscovite Muscovite is a common rock forming mineral and is found in igneous,…

N

Namaqa-Natal Belt The 'Kheisian' fabric is an early phase of the Mesoproterozoic evolution of… Natal Group The first sedimentary sequence deposited on the new basement was the Cambrian…

O

Orthoclase Orthoclase is a polymorph of other minerals that share the same chemistry,…

P

Pietersburg Group The Pietersburg Greenstone Belt occurs near the northern margin of the… Pyrite Pyrite is the classic "Fool's Gold". There are other shiny brassy yellow…

Q

Quartz Quartz is the most common mineral on the face of the Earth. It is found in… Quartzite The rock, which chiefly composed of quartz, is the metamorphic product of a…

R

Rocks Rocks are defined as any mass of mineral matter, whether consolidated or not,… Rose Quartz The pink to rose red colour is completely unique, unlike any other pink…

S

Sandstone Consist mostly of quartz with subsidiary amounts of feldspar, rock fragments… Sedimentary Deposits Summarised from Hydrogeology of the Main Karoo Basin: Current Knowledge and… Shale This is a laminated clay-rich rock. Fractures parallel to the bedding… Siltstone The rock consists of very fine-grained quartz and feldspar interlayered with… Slate This rock consists chiefly of clay minerals with subsidiary amounts of quartz… Smoky Quartz Smoky quartz is a popular variety of quartz. It has an unusual colour for a… Sphalerite Sphalerite, is an important ore of zinc. It can have excellent luster and…

T

Tertiary deposits South Africa Taken from http://www.geology.ukzn.ac.za During the Cenozoic sea-level began… Tiger's Eye Tiger's Eye is a chatoyant gemstone that is usually yellow- to red-brown,… Transvaal Supergroup Consists of major lithologies are (1) limestone and dolomite, (2) shale and… Tuff The rock is of volcanic origin and consists of volcanic glass, feldspar,…

V

Ventersdorp Supergroup The Ventersdorp Supergroup is dominated by andesitic lavas interlayerd with…

W

Waterberg Supergroup (and Soutpansberg Group) The underlying rock formation derives from the Kaapvaal craton, formed as a… Witwatersrand Supergroup Sedimentary deposition across the stable granite-gniess basement commenced…

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