Astrophyllite

Big Photo

Russia
3.13 carats
© raregemhunter

Astrophyllite is named after Greek "astron" - brilliant (star), plus "phyllon" - a leaf, alluding to its high lustre and foliate habit.

Astrophyllite is usually opaque to translucent, but may be transparent, brown to golden-yellow colour.

Astrophyllite is often cut into slabs and polished. It is sometimes used in jewelry where it is fashioned into cabochons.

Astrophyllite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
General Information
Chemical Formula
(K,Na)
 
3
(Fe
2+
 
,Mn)
 
7
Ti
 
2
Si
 
8
O
 
24
(O,OH)
 
7
Anthony et al, Handbook of mineralogy (2001)
Photos of natural/un-cut material from mindat.org
Physical Properties of Astrophyllite
Mohs Hardness3
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity3.2 to 3.4
Anthony et al, Handbook of mineralogy (2001)
TenacityBrittle
Anthony et al, Handbook of mineralogy (2001)
Cleavage QualityPerfect,Poor
Anthony et al, Handbook of mineralogy (2001)
Optical Properties of Astrophyllite
Refractive Index1.678 to 1.758
Anthony et al, Handbook of mineralogy (2001)
Optical CharacterBiaxial/+
Anthony et al, Handbook of mineralogy (2001)
PleochroismStrong: deep orange-red - orange-yellow - lemon-yellow
Anthony et al, Handbook of mineralogy (2001)
DispersionStrong
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)Bronze-yellow to gold-yellow, brown to reddish brown
Anthony et al, Handbook of mineralogy (2001)
TransparencyTranslucent,Opaque
Anthony et al, Handbook of mineralogy (2001)
LustrePearly,Greasy,Submetallic
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Astrophyllite
Crystal SystemTriclinic
Anthony et al, Handbook of mineralogy (2001)
HabitCrystals tabular, bladed or acicular, some faces commonly striated, to 10 cm; groups may be stellate
Anthony et al, Handbook of mineralogy (2001)
Geological Environment
Where found:In nepheline syenites, alkali granites, and their pegmatites; less commonly in fenites and other metasomatized rocks; in nepheline syenite gneisses and paragneisses
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Astrophyllite information at mindat.org
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