El término monacita se usa para designar a un grupo de cuatro minerales distintos, de la clase 8 de los minerales fosfatos según la clasificación de Strunz. Es, junto a la bastnasita, la principal mena de tierras raras. Aparece normalmente en forma de pequeños cristales aislados de color pardo rojizo. Fue descrito por Johann August Friedrich Breithaupt en 1829. El nombre monacita proviene del griego μοναζειν «monozoos», 'estar solo', en alusión a lo raro del mineral.

Leer el artículo completo en Wikipedia · CC-BY-SA

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: \n* Monazite-(Ce), (Ce, La, Nd, Th)PO4 (the most common member) \n* Monazite-(La), (La, Ce, Nd)PO4 \n* Monazite-(Nd), (Nd, La, Ce)PO4 \n* 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. 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.

Leer el artículo completo en Wikipedia · CC-BY-SA