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The Mineral Semarskite

semarskite mineral

Semarskite is a velvety black mineral of complex composition. It occurs in granite pegmatites. It is a mixture of several rare- earth metals with tantalum oxide and niobium.  Samaskite is one of several rare earth oxides. It is used as a source of uranium and rare earth elements. The leftover elements, seems not to want to form rare earth oxide. Rare earth oxides like Fergusonite and Euxenite have properties similar to samarskite and are associated with each other. Samarskite is a radioactive mineral and should be stored away from other minerals. Samarskite is associated with Feldspars, Tantalite, Quartz and other minerals. This mineral   has a potential to be a valuable resource. It can be cut into beautiful gems and used as cabochons.

Occurrence
Samarskite occurs in rare earth rich granite. It's also found in slow cooling igneous intrusive rocks.  It occurs in the Ural Mountains of Russia. It is also found in Iceland, Norway, Sweden, Brazil, North Carolina, California and USA.

Chemical Formula
(Y,Fe+++,U)(Nb,Ta)504

Derivation Of Name
In 1847, samarskite was first described for  occurrence in Miass. In 19th century samarskite was named after colonel von samarski, Russian inspector of mines. The original name of samarskite mineral is samarskite-(Y) Y is for the yttrium.

Physical Characteristics

Color is dark pitchy.

Transparency: crystals are opaque

Luster is vitreous and fresh surfaces have a submetallic luster.

The streak is reddish brown.

Fracture is conchoidal.

Cleavage is poor in one direction.

Hardness is 5-6.

Crystal system is orthorhombic.

Specific gravity is 4.3-5.87 (approximately) heavy for non-metallic minerals.

Geology
Samaraskite mineral lies in the middle town of pegmatite district of Connecticut. In the middle town area London describes the geochemical zonation of pegmatites.

Varieties Of Samarskite
Calciosamarskite is a calcium rich variety of samarskite whereas Ishikawaite is a uranium rich variety of samarskite. These minerals are completely metamict, chemically complex. The A site of samarskite-(Y) is dominated by Y+REE, the A site of ishikawaite is dominated by U+Th and the Calciosamarskite is dominated by ca.

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