monazite

(redirected from monazites)
Also found in: Dictionary, Thesaurus.

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.
..... Click the link for more information.
, 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.
..... Click the link for more information.
 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.
..... Click the link for more information.
 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.
..... Click the link for more information.
. 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 ?
1778 [+ or -] 2 Ma for monazite and 1728 [+ or -] 24 Ma for garnet, are clearly younger than any comparable results from Finland.
Textural, chemical and isotopic insights into the nature and behaviour of metamorphic monazite.
Constraints on the diffusivity of Pb in monazite, its closure temperature, and its U-Th-Pb systematics in metamorphic terrains, from a TIMS and SIMS study.
U-Pb age data on zircon and monazite of Estonian granulites Analysed Sample U, Pb, mineral/fraction, weight, ppm ppm mm mg Konnu 3005150 Opx-Gr-gneiss: 3005150A + 4.
Hiroshi Ikeda, 84, head of the organization, reportedly imported 40 tons of monazite from Thailand about 20 years ago for research and sale to hot springs that use radium and thorium.
The Sawara assemblyman allegedly told police investigators that he was not aware that the monazite he was holding was collateral for 5 million yen he loaned to Ikeda 15 years ago but he had no knowledge that it was monazite.
Police said the monazite was found stacked inside a storage room about 30 meters away from the assemblyman's house.
A sample of monazite from Llallagua, Bolivia (H110663) was also examined on the spindle stage and yielded a 2V of 25(2) [degrees] with indices of refraction equal to those reported in Palache et al.
Both distributions fall within their respective fields for REE in allanite and in monazite in metamorphic rocks as displayed by Grauch (1989).
Our LASS measurements show that Kangmar monazites have negative Eu anomalies and mild Y+HREE suppression produced by the presence of?
23) Monazite is a mineral with the formula (Ce, La, Nd,