allanite
allanite crystals of Mary Kathleen mine in Queensland, Australia
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
APPROACHING GEMS
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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