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Allanite

>> Group(s) : silicates
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Named by Thomas Thomson in 1810 after the scottish mineralogist Thomas Allan. This is a mieral close to epidote and there are 3 types of allanite based on their concentration in cerium, lanthanum, yttrium (rare earth element). The lanthanum variety is radioactive.

Exploited sites

Allanite is found all over the world : Canada, United States, Russia, Germany, Norway, Sweden, Japon, Italy.

See pictures of the mines / other pictures

Use in jewelry

Used only as a collector gem, sometimes faceted.

Daily care and precautions

Caution, natural radioactivity is possible, allanite may be kept away from people and kept in protective packaging.

Looking alike stones

cassiterite , sphalerite , tantalite

Chemical characteristics
(Ce,Ca,Y)2(Al,Fe)3[SiO4]3(OH)

aluminium sorosilicate, iron and rare earth element

Physical characteristics

Main color : brown

Other colors : yellow, black, green

brown is dominant, yttrium variety is black, opaque

Color of streak : brown, grey

Luster : vitreous, resinous

Hardness : 5.5 to 6.5

Density : 3.50 to 4.20

Cleavage : indistinct

Fracture : conchoidal, uneven

Optical properties

Transparency : transparent, translucent

Refractive Index : 1.710 - 1.820

Double refraction : 0.010

Biaxial (-)

visible double refraction : no

Dispersion : nette

Pleochroism : variable

Number of colors : 3

Only the variety containing lanthanum is strongly dichroic green, yellow green. Only two colors are clearly visible.

Fluorescence : none

Crystals

Prismatic

cristaux

Crystal system : monoclinic

Other informations
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