montebrasite
montebrasite crystal from U.S.
Detailed sheet
montebrasite
Close to amblygonite, ows its name to Montebras in France, in the Creuse.
The majority of gems called “amblygonite” are chemically closer to the “ montebrasite “.
CHEMICAL CHARACTERISTICS
LiAL[PO4] (OH)
lithium aluminium phosphate
PHYSICAL CHARACTERISTICS
Main color
colourless
Other colors
white, blue, yellow, green
Color of streak
white
Luster
greasy, pearly, vitreous
Hardness
5.5 to 6.0
Density
2.98 to 3.13
Cleavage
perfect
Fracture
conchoidal, uneven
pearly on the cleavage
OPTICAL PROPERTIES
Transparency
translucent, transparent
Refractive index
1.595 - 1.645
Double refraction
0.020
definite, biaxial (+/-)
visible double refraction
Yes
Dispersion
0.013(0.008)
Pleochroism
absent
Number of colors
1
Fluorescence
variable
sometimes blue to yellow green
CRYSTALS PROPERTIES
short prismatic
crystals system
triclinic
OTHER INFORMATIONS
APPROACHING GEMS
Exploited
sites
It is found in Brazil, Zaire, Burma, Spain, Austria, England.
use in jewelry
it is cut in facets.
Stones of a light color.
imitations and
treatments
It can undergo radiation treatments and then it takes a green, green-lemon yellow or blue tint. The color is stable in the light but disappears if the stone is heated.
Other
Gems
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