General Information:
Chemical Formula:
NaNa2(Fe++4Fe+++)Si8O22(OH)2
Composition:
(Molecular Weight = 958.89 gm)
Sodium 7.19 % Na
Iron 29.12 % Fe
Silicon 23.43 % Si
Hydrogen 0.21 % H
Oxygen 40.04 % O
Empirical Formula:
Na3Fe-2+4Fe-3+(Si8O22)(OH)2
Environment:
Igneous syenites and pegmatites.
IMA Status:
Approved IMA 1978
Locality:
Boulder Co., Colorado.
Name Origin:
Named after the Swedish chemist, J. A. Arfvedson (1792-1841).
Physical Properties:
Cleavage:
[110] Perfect, [???] Imperfect
Color:
black, grayish green, or bluish gray.
Density:
3.44 - 3.45, Average = 3.44
Diaphaniety:
Translucent to opaque
Habits:
Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Fibrous - Crystals made up of fibers., Stellate - Occurs as spherical, radial aggregates radia ting from a "star" like point.
Hardness:
5.5-6 - Knife Blade-Orthoclase
Luminescence:
Non-fluorescent.
Luster:
Vitreous (Glassy)
Streak:
bluish gray
More details...