monazite


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monazite

(mŏn`əzīt), yellow to reddish-brown natural phosphate of the rare earthsrare earths,
in chemistry, oxides of the rare-earth metals. They were once thought to be elements themselves. They are widely distributed in the earth's crust and are fairly abundant, although they were once thought to be very scarce.
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, mainly the ceriumcerium
[from the asteroid Ceres], metallic chemical element; symbol Ce; at. no. 58; at. wt. 140.116; m.p. 799°C;; b.p. 3,426°C;; sp. gr. 6.77 at 25°C;; valence +3 or +4. Cerium is a soft, malleable, ductile, iron-grey metal with hexagonal or cubic crystalline structure.
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 and lanthanumlanthanum
[Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.90547; m.p. about 920°C;; b.p. about 3,460°C;; sp. gr. 6.19 at 25°C;; valence +3.
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 metals, usually with some thoriumthorium
[from Thor], radioactive chemical element; symbol Th; at. no. 90; mass number of most stable isotope 232; m.p. about 1,750°C;; b.p. about 4,790°C;; sp. gr. 11.7 at 20°C;; valence +4.

Thorium is a soft, ductile, lustrous, silver-white, radioactive metal.
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. Yttrium, calcium, iron, and silica are frequently present. Monazite sand is the crude natural material and is usually purified from other minerals before entering commerce. Monazite occurs in North Carolina, South Carolina, Idaho, Colorado, Montana, and Florida in the United States, and in Brazil, India, Australia, and South Africa. It is an important source of cerium, thorium, and other rare-earth metals and compounds.

Monazite

 

a mineral; a phosphate of rare earths (mainly of the cerium group) with the chemical formula (Ce, La,…) [PO4]. It often contains various impurities, the most important of which are ThO2 (10 percent and more), UO2 (up to 6.6 percent), ZrO2, CaO, SiO2, and SO3.

Monazite crystallizes in a monoclinic system to form lamellar or sometimes thick tabular crystals, as well as irregular grains and grainy masses. The crystal structure of monazite is characterized by isolated [PO4]3− groups bonded to TR3+ ions in enneadic coordination. It is usually highly radioactive. Its color ranges from yellow or yellow-green to cinnamon and reddish brown. Hardness on the mineralogical scale, 5.0–5.5; density 4,900–5,500 kg/m3, depending on chemical composition.

Monazite deposits are usually associated with granitic pegmatites, less frequently with hydrothermal carbonate veins occurring in alkaline granites and syenites. It is extracted mainly from alluvial deposits in rivers and oceans (for example, in India, Sri Lanka, and Brazil), where it settles during erosion of granite and gneiss containing monazite as an accessory mineral. It is a raw material in the isolation of cerium and thorium.

G. P. BARSANOV

monazite

[′män·ə‚zīt]
(mineralogy)
A yellow or brown rare-earth phosphate monoclinic mineral with appreciable substitution of thorium for rare-earths and silicon for phosphorus; the principal ore of the rare earths and of thorium. Also known as cryptolite.
References in periodicals archive ?
Monazite crystals occur as subhedral to anhedral and almost rounded grains ranging from very small up to 100 [micro]m in diameter and are mostly in contact with other accessory minerals, such as Fe-Ti oxides, zircon, and apatite (Fig.
It should also be taken into account that North Korea delivered 15,000,000 kilograms of monazite concentrate when today's annual global yield of this material amounts to 12,000,000 kilograms.
In fact, every year thousands of tourists flock to beaches such as Guarapari, Brazil, where radioactive monazite sands, famous for their healing qualities, deliver almost 88 times the average background dose people receive in the United States.
Thorium occurs in minerals, predominantly in thorium-phosphate and monazite, which contains 12% thorium oxide [1].
Part of it's plan comprises of an overall production strategy to utilise supplies of monazite available in the Gulf region, the company said.
Bastnaesite occurs as a primary mineral, while monazite is found
Monazite sampling exceeded 48%-50%, and valuable heavy minerals included zircon, leucoxene and ilmenite.
while the second largest portion is comprised of monazite deposits in Australia, Brazil, China, India, Malaysia, South Africa, Sri Lanka, Thailand, and the U.
The country has reserves of monazite, a type of rare earth, in Bahia state in the country's northeast.
The monazite is said to come from the Ch'olsan Uranium Mine near Ch'olsan-kun in P'yong'an Province.
With regard to the comments about Brazil, it is true that some, but by no means all, beaches contain radioactive monazite deposits.