Most elements need to be concentrated into amounts that can be economically mined from ore deposits (usually hundreds to thousands of times their crustal abundance). This concentration is usually accomplished by dissolution of the element by hot water (hydrothermal ore deposits - gold, silver, lead), preferential crystallization from magmas (chromite deposits or pegmatites), surface weathering and leaching (aluminum, nickel, copper), or gravity separation of minerals during erosion (gold, diamonds, titanium). In the majority of cases there are only one or two minerals that provide all of a particular element for commercial uses. Some elements in low concentrations (substituting in minor amounts for the major elements) are associated with minerals that are mined for other elements, but the shear volumes of materials that are processed result in a valuable byproduct (i e. elements associated with copper, lead, and zinc ores). Some elements are so valuable that almost any mineral containing that element in sufficient grades can be mined (gold, silver, platinum group).
ELEMENTS
Aluminum - The ore is mined from rocks that have been exposed to weathering in a tropical environment, bauxite. The main ore minerals in bauxite are gibbsite, bohmeite, and diaspore.
Antimony - The primary ore of antimony is it's sulfide, stibnite.
Arsenic - Recovered from other metal processing streams (primarily from the sulfosalts such as tennantite etc.). Arsenopyrite is the most common arsenic mineral. The relatively low demand for arsenic as compared to the amount of arsenic mined that is associated with other metals means it can be supplied from the waste streams of other ore processing.
Barium - The chief source of barium is barite with minor production of witherite.
Beryllium - The major ore mineral for beryllium in the U.S. is bertrandite while worldwide the major source is from pegmatites that contain beryl.
Bismuth - Primarily a byproduct of lead processing. Also found in a number of minerals such as bismuthinite and as a constituent in various sulfosalts.
Boron - Chief source is playa lake deposits of borax, colemanite, kernite, ulexite.
Bromine - Chief sources are brines from wells and Dead Sea.
Cadmium - Unlike many other commodities cadmium is produced as a byproduct of zinc (sphalerite) mining.
Cesium - The major ore mineral is pollucite, a pegmatite mineral. Production and use of this metal is extremely small (a few thousand kilograms per year).
Chlorine - Produced from the mineral halite (rock salt).
Chromium - The chief source is the mineral chromite which is found in large layered intrusives and serpentine bodies.
Cobalt - The primary minerals for cobalt is cobaltite. Some cobalt is also produced from weathered tropical orebodies.
Columbium (see Niobium)
Copper - Most copper ore bodies are mined from minerals created by weathering of the primary copper ore mineral chalcopyrite. Minerals in the enriched zone include chalcocite, bornite, djurleite. Minerals in the oxidized zones include malachite, azurite, chyrsocolla, cuprite, tenorite, native copper and brochantite.
Gallium - A byproduct of zinc and alumina processing. Some primary "ore" may contain up to 200 ppm. Ga.
Germanium - A byproduct of zinc ore processing. Also a deposit in China is associated with coal.
Gold - The primary mineral of gold is the native metal and electrum (a gold-silver alloy). Some tellurides are also important ore minerals such as calaverite, sylvanite, and petzite.
Hafnium - Primary ore mineral is zircon.
Indium - Primarily is a byproduct of zinc processing.
Iodine - Initial production was from seaweed. Iodine is extracted from natural gas field brines (up to 1200 ppm iodine in the brines).
Iron - Two major minerals in the production of iron are it's oxides, hematite and magnetite. These are found in preCambrian iron formations. Historically there was also production from goethite and siderite. The iron sulfides (pyrite and pyrrhotite) were not used as iron sources due to the difficulty of removing sulfur from the metals and the brittleness this sulfur caused in the metal.
Lead - The primary ore mineral for lead is it's sulfide - galena. Some minor production from the past has come from secondary lead minerals - cerussite and anglesite.
Lithium - The former primary ore minerals were pegmatite deposits of spodumene, lepidolite, and petalite, amblygonite. Currently the major U. S. production is from lithium carbonate brines.
Magnesium - Although magnesium is found in many minerals, only dolomite, magnesite, brucite, carnallite, and olivine are of commercial importance. Magnesium and other magnesium compounds are also produced from seawater, well and lake brines and bitterns.
Manganese - The primary ores are oxides/hydroxides of manganese which include minerals such as hausmannite, pyrolusite, braunite, manganite, etc. and the carbonate, rhodochrosite. A large potential source is the deep sea manganese nodules.
Mercury - The main ore is the sulfide, cinnabar.
Molybdenum - The primary ore mineral is molybdenite.
Nickel - The primary nickel ores are pentlandite, nickel bearing pyrrhotite and a weathering product, garnierite (a mixture of népouite, pecoraite and willemseite).
Niobium (Columbium) - The primary ore mineral is pyrochlore with minor columbite and tantalite-columbite.
Phosphorus - Main ore minerals are in the apatite group of minerals (hydroxylapatite, fluorapatite, chlorapatite).
Platinum group (Platinum, Osmium, Rhodium, Ruthenium, Palladium) - The primary ores are the native elements or alloys of the various elements or arsenides such as sperrylite. They tend to occur in layered intrusives associated with chromite deposits.
Potassium (potash) - The primary ore minerals are sylvite (primarily), brines, and langbeinite.
Rare Earth elements (cerium, dysprosium, erbium, europium, gadolinium, holmium, lanthanium, lutetium, neodymium, praseodymium, samarium, scandium, terbium, thulium, ytterbium, yttrium) The major ore minerals containing rare earth elements are bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. Major U.S. production of bastnesite is from Mountain Pass, California.
Rhenium - Produced as a byproduct of molybdenite.
Rubidium - Substitutes for potassium in lepidolite and pollucite. Production is small (a few thousand kilograms per year).
Scandium (see Rare Earth)
Selenium - Recovered from copper processing.
Silicon - The primary source is quartz.
Silver - Silver production has been from the sulfide argentite/acanthite, native silver, sulfosalts such as pyrargyrite and proustite, chloride as cerargyrite. It is also found in small amounts in some tetrahedrites.
Sodium - Principle resources are halite (rock salt) or soda ash (see below).
Strontium - Main ore mineral is celestite, with minor production of strontianite.
Sulfur - Major production is from desulferizing natural gas and petroleum. Sulfuric acid is produced from the flue gases of metal smelters. Historically, sulfur was produced from native sulfur and pyrite.
Tantalum - Primarily from tantalite-columbite although minor amounts are found in tin concentrates.
Tellurium - Recovered in processing copper ores.
Thallium - Recovered from processing copper, lead and zinc ores.
Thorium - Recovered primarily from monazite.
Tin - Primary ore is cassiterite.
Titanium - Usually produced from placer deposits, the ore minerals are rutile, ilmenite, and leucoxene.
Tungsten - Primary ore minerals are scheelite and huebnerite-ferberite.
Uranium - The chief primary ore minerals are uraninite, pitchblende (a mixture of various oxides), coffinite and a host of secondary minerals such as carnotite and autunite.
Vanadium - Recovered from petroleum residues also produced from vanadium bearing magnetite rocks. In the past it was recovered from minerals in uranium deposits.
Zinc - The primary zinc ore mineral is sphalerite, zinc sulfide. Some past production has been from smithsonite and hemimorphite.
Zirconium - Major source is the mineral zircon.
INDUSTRIAL MINERALS
Abrasives, natural - Diamonds, garnets (almandine, pyrope and andradite), corundum (emery).
Barite - A major use for barite is as a weight increasing additive for drilling oil and gas wells.
Calcite - A major source for this mineral is limestone. It has been used for the manufacture of cement, application to agricultural lands for pH control, as a building material, and crushed for gravel.
Clays - Used in the manufacture of bricks, tiles and as a filler for paper etc.
Attapulgite
Ball Clay
Bentonite
Calcium Bentonite
Common Clay
*Minerals Fire Clay
Hectorite*
Kaolinite*
Meerschaum
Palygorskite*
Refractory Clay
Saponite*
Sepiolite*
Shale
Sodium Bentonite
Feldspars - Used in manufacture of glass, ceramics and enamels. Includes orthoclase, microcline, and albite (member of the plagioclase series).
Gemstones - The most valuable total gemstone production is diamond; corundum varieties, ruby and sapphire; beryl varieties emerald, aquamarine, and kunzite. Many other semiprecious gemstones are mined for decorative and jewelry use.
Gypsum - A major source for Portland cement, plaster of Paris, a soil conditioner, and an important component in drywall.
Perlite - Used in lightweight aggregates.
Soda Ash (sodium carbonate) - Primary production from trona, nahcolite and brines.
Zeolites - The primary natural production of zeolites include the minerals chabazite, clinoptilolite, and mordenite.
Miscellaneous mineral production - wollastonite, vermiculite, talc, pyrophyllite, graphite, kyanite, andalusite, muscovite, and phlogopite.
For more information see the United States Geological Survey website on mineral production (the source for most of this information).
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Copyright © 1997 - 2009 Mineralogical Society of America. All rights reserved
Friday, November 6, 2009
Uranium ore formation
All ores are formed by geological processes. The clarke (Chapter 10) for uranium is about
4 mmol/mol (4 parts per million). Obviously, ore bodies have a higher concentration:
uraninite is 50 to 80% uranium, while davidite is only around 10% uranium. There are
roughly half dozen basic ore formation processes, of which the four most important for
uranium are:
1. sedimentary accumulation,
2. diagenesis,
3. magmatic segregation, and
4. hydrothermal circulation.
Sedimentation can occur in several ways. Limestone is formed by the rain of small marine
organisms onto the ocean bottom, and salt is formed when an interior sea dries up and is
covered by aolian deposits. In the case of gold, silver, uranium, and thorium, for example,
microscopic pieces could be carried off as runoff. In certain areas where the water stilled,
for example, a lake or widening of a stream, the denser pieces could fall to the lakebed or
streambed.
Diagenesis refers to chemical and physical changes that occur after deposition. If oxygen
is available, an element might combine with it to form an oxide. The oxide might replace
another compound, or, alternatively, if oxygen is removed, a sulfur atom could replace an
oxygen atom. Since the uranium-laced sediment might be covered by more sediment, it
could be subject to such chemical changes.
Magma is liquid rock. There could be ores formed by “freezing out” of materials by their
differing melting temperatures. The resulting ore bodies could rise or sink relative to the
Energy, Ch. 19, extension 4 Uranium ore formation 2
liquid depending on its density.
In hydrothermal circulation, hot water flowing can cause chemical changes and cause
migration of materials to help form ore bodies. This mechanism is less important for
uranium than for copper, silver, and gold ore formation.
Magmatic segregation is often involved in formation of uranium-rich rock. The uranium
may or may not be acted on by hot water (hydrothermal circulation) or hot gases during
its formation. In any case, volcanic action and other geological processes can cause regions
of uranium-bearing rock at concentrations higher then the clarke. As Earth’s plates move,
these original low-concentration rocks may be exposed and eroded by weathering. Water
can carry off the small pieces of rock, including uranium.
In the case of the Oklo deposit in Gabon,(29) not atypical of uranium ore formation, the
area that contained the ore that formed the natural reactor was originally a river delta.
When archaeobacteria began making the oxygen atmosphere, the exposed uranium became
oxidized. The oxidized uranium was weathered, traveled to the delta, and became encased
in the bottom ooze, where the uranium exchanged its oxygen for other elements. The
densest metals had accumulated in bottom sediments, and as these became overlain with
more sediments, the pressure eventually made sandstone out of the buried ooze.
The original volcanic rock containing low concentrations of uranium had become
sedimentary rock with higher concentrations. Geological processes compressed the
sandstone further, then uplifted and folded the rock. Water circulated among the broken
pieces of rock and helped the uranium gather in richer pockets. These were again overlain
and compressed, forming the ore body. This ore body was enriched compared to the
sandstone, and therefore greatly enriched compared to the original volcanic rock. It
Energy, Ch. 19, extension 4 Uranium ore formation 3
contained enough uranium (of course with high enough concentration of uranium-235) to
allow the natural Oklo reactor to run (see the box on this unique event in the chapter).
Uranium ore formations elsewhere also involved these four processes. Most ores seem to
be near regions that had experienced magmatic intrusions of volcanism in the distant past.
This is consistent with what happened in Oklo, Gabon.
Herndon argues that Earth contains an operating reactor. As radioactive decay decreases
the amount of uranium-235 relative to uranium-238, the reactor is going to turn off
eventually. He thinks that the georeactor runs Earth’s magnetic field.(30) In this case, if it
turns off sometime within the next several million years, it would have strong impacts on
Earth.
4 mmol/mol (4 parts per million). Obviously, ore bodies have a higher concentration:
uraninite is 50 to 80% uranium, while davidite is only around 10% uranium. There are
roughly half dozen basic ore formation processes, of which the four most important for
uranium are:
1. sedimentary accumulation,
2. diagenesis,
3. magmatic segregation, and
4. hydrothermal circulation.
Sedimentation can occur in several ways. Limestone is formed by the rain of small marine
organisms onto the ocean bottom, and salt is formed when an interior sea dries up and is
covered by aolian deposits. In the case of gold, silver, uranium, and thorium, for example,
microscopic pieces could be carried off as runoff. In certain areas where the water stilled,
for example, a lake or widening of a stream, the denser pieces could fall to the lakebed or
streambed.
Diagenesis refers to chemical and physical changes that occur after deposition. If oxygen
is available, an element might combine with it to form an oxide. The oxide might replace
another compound, or, alternatively, if oxygen is removed, a sulfur atom could replace an
oxygen atom. Since the uranium-laced sediment might be covered by more sediment, it
could be subject to such chemical changes.
Magma is liquid rock. There could be ores formed by “freezing out” of materials by their
differing melting temperatures. The resulting ore bodies could rise or sink relative to the
Energy, Ch. 19, extension 4 Uranium ore formation 2
liquid depending on its density.
In hydrothermal circulation, hot water flowing can cause chemical changes and cause
migration of materials to help form ore bodies. This mechanism is less important for
uranium than for copper, silver, and gold ore formation.
Magmatic segregation is often involved in formation of uranium-rich rock. The uranium
may or may not be acted on by hot water (hydrothermal circulation) or hot gases during
its formation. In any case, volcanic action and other geological processes can cause regions
of uranium-bearing rock at concentrations higher then the clarke. As Earth’s plates move,
these original low-concentration rocks may be exposed and eroded by weathering. Water
can carry off the small pieces of rock, including uranium.
In the case of the Oklo deposit in Gabon,(29) not atypical of uranium ore formation, the
area that contained the ore that formed the natural reactor was originally a river delta.
When archaeobacteria began making the oxygen atmosphere, the exposed uranium became
oxidized. The oxidized uranium was weathered, traveled to the delta, and became encased
in the bottom ooze, where the uranium exchanged its oxygen for other elements. The
densest metals had accumulated in bottom sediments, and as these became overlain with
more sediments, the pressure eventually made sandstone out of the buried ooze.
The original volcanic rock containing low concentrations of uranium had become
sedimentary rock with higher concentrations. Geological processes compressed the
sandstone further, then uplifted and folded the rock. Water circulated among the broken
pieces of rock and helped the uranium gather in richer pockets. These were again overlain
and compressed, forming the ore body. This ore body was enriched compared to the
sandstone, and therefore greatly enriched compared to the original volcanic rock. It
Energy, Ch. 19, extension 4 Uranium ore formation 3
contained enough uranium (of course with high enough concentration of uranium-235) to
allow the natural Oklo reactor to run (see the box on this unique event in the chapter).
Uranium ore formations elsewhere also involved these four processes. Most ores seem to
be near regions that had experienced magmatic intrusions of volcanism in the distant past.
This is consistent with what happened in Oklo, Gabon.
Herndon argues that Earth contains an operating reactor. As radioactive decay decreases
the amount of uranium-235 relative to uranium-238, the reactor is going to turn off
eventually. He thinks that the georeactor runs Earth’s magnetic field.(30) In this case, if it
turns off sometime within the next several million years, it would have strong impacts on
Earth.
Properties and Classification
Properties of the clays include plasticity, shrinkage under firing and under air drying, fineness of grain, color after firing, hardness, cohesion, and capacity of the surface to take decoration. On the basis of such qualities clays are variously divided into classes or groups; products are generally made from mixtures of clays and other substances. The purest clays are the china clays and kaolins. "Ball clay" is a name for a group of plastic, refractory (high-temperature) clays used with other clays to improve their plasticity and to increase their strength. Bentonites are clays composed of very fine particles derived usually from volcanic ash. They are composed chiefly of the hydrous magnesium-calcium-aluminum silicate called montmorillonite. See also fuller's earth.
Individual clay particles are always smaller than 0.004 mm. Clays often form colloidal suspensions when immersed in water, but the clay particles flocculate (clump) and settle quickly in saline water. Clays are easily molded into a form that they retain when dry, and they become hard and lose their plasticity when subjected to heat.
Individual clay particles are always smaller than 0.004 mm. Clays often form colloidal suspensions when immersed in water, but the clay particles flocculate (clump) and settle quickly in saline water. Clays are easily molded into a form that they retain when dry, and they become hard and lose their plasticity when subjected to heat.
how clays formed
Formation
Clays are divided into two classes: residual clay, found in the place of origin, and transported clay, also known as sedimentary clay, removed from the place of origin by an agent of erosion and deposited in a new and possibly distant position. Residual clays are most commonly formed by surface weathering, which gives rise to clay in three ways-by the chemical decomposition of rocks, such as granite, containing silica and alumina; by the solution of rocks, such as limestone, containing clayey impurities, which, being insoluble, are deposited as clay; and by the disintegration and solution of shale. One of the commonest processes of clay formation is the chemical decomposition of feldspar.
Clay consists of a sheet of interconnected silicates combined with a second sheetlike grouping of metallic atoms, oxygen, and hydroxyl, forming a two-layer mineral such as kaolinite. Sometimes the latter sheetlike structure is found sandwiched between two silica sheets, forming a three-layer mineral such as vermiculite. In the lithification process, compacted clay layers can be transformed into shale. Under the intense heat and pressure that may develop in the layers, the shale can be metamorphosed into slate.
Clays are divided into two classes: residual clay, found in the place of origin, and transported clay, also known as sedimentary clay, removed from the place of origin by an agent of erosion and deposited in a new and possibly distant position. Residual clays are most commonly formed by surface weathering, which gives rise to clay in three ways-by the chemical decomposition of rocks, such as granite, containing silica and alumina; by the solution of rocks, such as limestone, containing clayey impurities, which, being insoluble, are deposited as clay; and by the disintegration and solution of shale. One of the commonest processes of clay formation is the chemical decomposition of feldspar.
Clay consists of a sheet of interconnected silicates combined with a second sheetlike grouping of metallic atoms, oxygen, and hydroxyl, forming a two-layer mineral such as kaolinite. Sometimes the latter sheetlike structure is found sandwiched between two silica sheets, forming a three-layer mineral such as vermiculite. In the lithification process, compacted clay layers can be transformed into shale. Under the intense heat and pressure that may develop in the layers, the shale can be metamorphosed into slate.
list 5 main clay mineral
Clay minerals include the following groups:
Kaolin group which includes the minerals kaolinite, dickite, halloysite and nacrite.[1]
Some sources include the serpentine group due to structural similarities (Bailey 1980).
Smectite group which includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite.[1]
Illite group which includes the clay-micas. Illite is the only common mineral.[1]
Chlorite group includes a wide variety of similar minerals with considerable chemical variation.[1]
Other 2:1 clay types exist such as sepiolite or attapulgite, clays with long water channels internal to their structure
Kaolin group which includes the minerals kaolinite, dickite, halloysite and nacrite.[1]
Some sources include the serpentine group due to structural similarities (Bailey 1980).
Smectite group which includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite.[1]
Illite group which includes the clay-micas. Illite is the only common mineral.[1]
Chlorite group includes a wide variety of similar minerals with considerable chemical variation.[1]
Other 2:1 clay types exist such as sepiolite or attapulgite, clays with long water channels internal to their structure
list 5 main clay mineral
Clay minerals include the following groups:
Kaolin group which includes the minerals kaolinite, dickite, halloysite and nacrite.[1]
Some sources include the serpentine group due to structural similarities (Bailey 1980).
Smectite group which includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite.[1]
Illite group which includes the clay-micas. Illite is the only common mineral.[1]
Chlorite group includes a wide variety of similar minerals with considerable chemical variation.[1]
Other 2:1 clay types exist such as sepiolite or attapulgite, clays with long water channels internal to their structure
Kaolin group which includes the minerals kaolinite, dickite, halloysite and nacrite.[1]
Some sources include the serpentine group due to structural similarities (Bailey 1980).
Smectite group which includes dioctahedral smectites such as montmorillonite and nontronite and trioctahedral smectites for example saponite.[1]
Illite group which includes the clay-micas. Illite is the only common mineral.[1]
Chlorite group includes a wide variety of similar minerals with considerable chemical variation.[1]
Other 2:1 clay types exist such as sepiolite or attapulgite, clays with long water channels internal to their structure
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