sellaite
sellaite crystals on quartz from Brumado, Bahia State, in Brazil
Detailed sheet
sellaite
Discovered in France in 1868, it honors the name of the Italian mineralogist Quintino Sella (1827-1884). This is a fluoride such as fluorite, but of magnesium.
CHEMICAL CHARACTERISTICS
MgF2
magnesium fluoride
PHYSICAL CHARACTERISTICS
Main color
colourless
Other colors
white
Color of streak
white
Luster
greasy, vitreous
Hardness
5.0 to 5.5
Density
3.10 to 3.20
Cleavage
perfect
Fracture
conchoidal
OPTICAL PROPERTIES
Transparency
transparent
Refractive index
1.378 - 1.391
Double refraction
0.012
weak uniaxial positive
visible double refraction
No
Dispersion
aucune
Pleochroism
absent
Number of colors
1
Fluorescence
none
CRYSTALS PROPERTIES
sometimes dipyramidal crystals
crystals system
tetragonal
OTHER INFORMATIONS
APPROACHING GEMS
Exploited
sites
The most beautiful crystals come from Brazil, Serra das Eguas, Bahia. It is also found in Zambia, Tanzania, Russia (Urals, Siberia), Italy and France in the Pyrenees (Prats de Mollo).
use in jewelry
It is cut in facets, the best ones come from Brazil
Other
Gems
Venez visitez
notre site web
voillot-joaillier.fr
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