Detailed sheet

allanite

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.



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

resinous, vitreous

Hardness

5.5 to 6.5

Density

3.50 to 4.20

Cleavage

indistinct

Fracture

conchoidal, uneven



OPTICAL PROPERTIES

Transparency

translucent, transparent

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 PROPERTIES

prismatic

crystals system

monoclinic



OTHER INFORMATIONS

Exploited
sites

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

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.

Other
Gems

Venez visitez

notre site web

voillot-joaillier.fr

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