A rare-earth mineral contains one or more rare-earth elements as major metal constituents. Rare-earth minerals are usually found in association with

alkaline In chemistry, an alkali (; from the Arabic word , ) is a basic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a soluble base has a pH greater than 7.0. The ...

to peralkaline igneous magmas in pegmatites or with

carbonatite Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...

intrusives. Perovskite mineral phases are common hosts to rare-earth elements within the alkaline complexes.

Mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s are solids composed of various inorganic elements, mixed through processes such as evaporation, pressure or other physical changes. Rare earth minerals are rare because rare earth elements have unique geochemical properties that prevent them from easily forming minerals, and are therefore not normally found in deposits large or concentrated enough for mining. This is the reason they are called "rare" earths. These elements have a wide range of uses from every day items to military technologies. The minerals that do exist are often associated with alkaline magmas or with

intrusives. Perovskite mineral phases are common hosts to rare-earth elements within the alkaline complexes. Mantle-derived carbonate melts are also carriers of rare earths. Hydrothermal deposits associated with alkaline magmatism contain a variety of rare-earth minerals. The following list includes the more common hydrothermal minerals that often contain significant rare earth elements: * aeschynite-(Ce) * aeschynite-(Y) * allanite *

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

* bastnäsite * britholite * brockite * cerite * dollaseite-(Ce) * fluocerite * fluorite * gadolinite * monazite * parisite-(Ce) * parisite-(La) * stillwellite * synchysite * titanite * wakefieldite * xenotime * zircon

Primary and secondary deposits

Primary deposits result from hydrothermal and igneous processes while secondary deposits are sedimentary and formed through weathering processes. In the case of primary deposits, the minerals are generally found in the specific location where the elements came together to form the deposit. Secondary deposits have undergone metamorphic or sedimentary processes in a location different from where the minerals were actually formed. Depending on the type of deposit, various methods can be employed to extract the minerals from both primary and secondary deposits.

Mined rare-earth minerals

Bastnäsite

Bastnäsite is a rare, semi-soluble carbonate mineral, primarily mined for its yttrium, used to make magnets for speakers, microphones, communication devices, and many other modern necessities. Bastnäsite deposits are found in China, Madagascar and the USA.

Laterite clays

Laterite is a class of materials which contain significant amounts of aluminium and iron. They can form clays able to hold many minerals within them. The weathering of rocks by leaching and oxidising conditions results in the formation of clay-like minerals such as

goethite Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α- polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient t ...

, lepidocrocite, and hematite. Some of them can hold rare earth minerals as well as iron, nickel and the alumina for which it is often mined. Laterite results from the weathering of basalt. It can make a stable basis for construction since it solidifies into rock when exposed to air. However, its low fertility makes it unsuitable for agricultural use.

Monazite

Monazite is a waxy mineral that is formed through the crystallization of igneous rocks and the metamorphism of clastic sedimentary rocks. This mineral is typically mined in placer deposits, with gold commonly found as a byproduct. Monazite contains many rare metals such as

neodymium Neodymium is a chemical element; it has Symbol (chemistry), symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth element, rare-earth metals. It is a hard (physics), hard, sli ...

, cerium, lanthanum, praseodymium, and samarium, making it a critical material for renewable energy devices. Monazite sand and deposits for mining are found in India, Brazil, and Australia.

Loparite

Loparite is a mineral that is mined for the three rare (but not rare earth) elements: titanium,

niobium Niobium is a chemical element; it has chemical symbol, symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and Ductility, ductile transition metal. Pure niobium has a Mohs scale of mineral hardness, Mohs h ...

, and

tantalum Tantalum is a chemical element; it has Symbol (chemistry), symbol Ta and atomic number 73. It is named after Tantalus, a figure in Greek mythology. Tantalum is a very hard, ductility, ductile, lustre (mineralogy), lustrous, blue-gray transition ...

it contains. Major Loparite deposits can be found in Russia and Paraguay,and although it is present in other countries such as Canada, Norway, Greenland, and Brazil, Russia remains the primary source for mining this mineral. The elements in loparite make it useful for conductivity, aircraft assembly, and as a radioactive tracer.

Rarity

Kyawthuite is a rare mineral because the extreme pressure needed for its formation is very uncommon. Unlike other minerals, it is created from a pegmatite deposit within an igneous rock. Its deep red-brown colour and high density come from the crystal assemblages within it. The mineral contains

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

and

thallium Thallium is a chemical element; it has Symbol (chemistry), symbol Tl and atomic number 81. It is a silvery-white post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Che ...

that have undergone oxidation, as well as the rare metals bismuth and

antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...

. The mineral is named after Kyaw Thu, a former geologist at the University of Yangon who discovered it. It is found in the region of Myanmar Mogok.

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