hornblende
Detailed sheet
hornblende
Very common mineral, its name comes from the German “horn” horn “blenden” dazzle.
There are many varieties depending on the content of iron, magnesium, calcium etc …
CHEMICAL CHARACTERISTICS
(Ca,Na,K)2(Mg,Fe,Al)5[Si6(Al,Si)2O22](OH,F)2
iron - magnesium inosilicate
PHYSICAL CHARACTERISTICS
Main color
brown
Other colors
black, green
Color of streak
grey, green
Luster
vitreous
Hardness
5.0 to 6.0
Density
2.72 to 2.90
Cleavage
perfect
Fracture
uneven
presence of elongated planar portions on the fracture
OPTICAL PROPERTIES
Transparency
opaque, translucent
Refractive index
1.675 - 1.695
Double refraction
0.020
definite, biaxial (-)
visible double refraction
No
Pleochroism
absent
Number of colors
1
Fluorescence
none
CRYSTALS PROPERTIES
prismatic
crystals system
monoclinic
OTHER INFORMATIONS
APPROACHING GEMS
Exploited
sites
It is found worldwide, mainly the Alps in Europe, Brazil, Arizona United States, Germany, Ethiopia, China, Egypt, Japan, Australia …
use in jewelry
transparent and clear varieties are cut in facets for collection
Other
Gems
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