Minerals ~ Monazite
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Monazite - Locality: Madagascar
Displayed in the Mineralogical Museum, Bonn, Germany
Credit: Ra'ike

Monazite is a reddish-brown phosphate mineral containing rare earth metals. It occurs usually in small isolated crystals. It has a hardness of 5.0 to 5.5 on the Mohs scale of mineral hardness and is relatively dense, about 4.6 to 5.7 g/cm3. There are at least four different kinds of monazite, depending on relative elemental composition of the mineral:
  • Monazite-(Ce), (Ce, La, Nd, Th)PO4 (the most common member)
  • Monazite-(La), (La, Ce, Nd)PO4
  • Monazite-(Nd), (Nd, La, Ce)PO4
  • Monazite-(Sm), (Sm, Gd, Ce, Th)PO4
The elements in parentheses are listed in the order of their relative proportion within the mineral: lanthanum is the most common rare earth element in monazite-(La), and so forth. Silica (SiO2) is present in trace amounts, as well as small amounts of uranium and thorium. Due to the alpha decay of thorium and uranium, monazite contains a significant amount of helium, which can be extracted by heating.[3]

Monazite is an important ore for thorium, lanthanum, and cerium. It is often found in placer deposits. India, Madagascar, and South Africa have large deposits of monazite sands. The deposits in India are particularly rich in monazite.

Monazite is radioactive due to the presence of thorium and, less commonly, uranium. Because of its radioactive nature, monazite is a useful for radiometric dating of geological events, such as crystallization, heating, or deformation of the rocks containing monazite.

The name monazite comes from the Greek μονάζειν (to be solitary), via German Monazit, in allusion to its isolated crystals.


Monazite Sand, Guarapari, Espírito Santo, Brazil

Naturally radioactive black sand on the beaches of Brazil. Below is a Youtube video showing the radioactive levels. "I'm a Brazilian physicist and I used to swim very often in this beach. Its name is "Praia da areia preta" (free translation would be: black sand beach)" - Sandro Boschetti

Monazite Sand, Guarapari, Espírito Santo, Brazil
Monazite : (Ce,Nd,Y,Dy,Sm,Nd,Th)(PO4), Ilmenite : Fe2+TiO3,
Magnetite : Fe2+Fe3+2O4, Rutile : TiO2, Quartz : SiO2
Source: Mindat.org

Brazil 2012: Sunbathing on Radioactive Beaches

Praia da Areia Preta Black Sand Beach, Brazil

It was Prof. Henry Gorceix, founder of Ouro Preto School of Mines, who first investigated the monazite sands in Brazil, as published in the annals of "School" in 1884 and 1885 and communication to the Academy of Sciences of Paris- France. Gorceix received samples of yellow sands of Caravelas Beach and Meadow in Bahia, which were sent by the geologist Orville Derby, the National Museum of Rio de Janeiro. These samples were collected by a sailboat commander of Firma E. Johnston & Co., that was sent to John Gordon engineer, director of the firm. Gordon possession of the results of the analysis sought to market for application, but only in 1886, when came the incandescent shirts AUER for gas lighting in which they were used lanthanum salts, yttrium, zirconium and magnesium Swedish minerals, then replaced by Tory of monazite sands of Brazil. ~ SOURCE

Brazil 2012: The Secret of the Radioactive Sand

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Mineral & Gemstone Chips in Mini Bottles

These little bottles contain top quality mineral and gemstone chips from our tailings. We high grade the material. Click on the image to see the full listing of available specimens

Price: Marked under Specimens

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