Ortit (Old Greek ὀρθός – straight, correct) is a rare mineral of the island structure of the epidote group of the silicate class. It was discovered in 1810 by the Scottish mineralogist Thomas Allan (1777-1833). It got its name in 1818 because of the prismatic shape of the crystals. It has many synonyms: allanite (in honor of the discoverer), bagrationite, bodenite, muromontite, tautotite, cerin, cerepidot.
Properties
Contains a significant amount of rare elements: Ce, La, Dy, Er, V. Chemical formula – (Ca, Ce, La, Y) 2 (Al, Fe) 3 (SiO4) 3 (OH). Percentage composition (in the Ural pegmatites): CaO – 10.43; Ce2O3 10.13; MnO 2.25; FeO 8.14; Fe2O3 – 6.29; MgO 0.13; Al2O3 16.25; SiO2 – 30.81; H2O 2.79. The color is brown to black. The gloss from the surface is often metallic or oily, and glassy in the fracture. Fracture fracture. Density 3.3-3.8. Hardness 5.5-6. Radioactive. Strong pleochroism (red-brown-brown-golden-green-brown). There is no luminescence.
The crystals are . It occurs mainly in crystalline silicate rocks: granites, gneisses, syenites, crystalline schists, usually in the form of grains.
Varieties
- beryllium orthite (contains up to 6% BeO);
- orthite-epidote (intermediate in composition between orthite and epidote);
- yttrium orthite (contains up to 8% Y2O3);
- magnesium orthite (contains up to 15% MgO);
- manganese orthite (contains up to 5.37% MnO);
- scandium orthite (contains up to 1% Sc2O3);
- (contains up to 5.6% ThO2);
- cerite orthite (contains up to 20% Сe2О3).
Application
It is an ore of rare earth metals and thorium. Prized by collectors. Due to its dark color, it is rarely used in jewelry.
Place of Birth
Locations of detection: Norway, Sweden, Finland, Ural (called Ural ortite), (Azov region), USA (California, Virginia), Canada, .
