Mineral Information and Data:

Ferrosilite
Fe2+2(SiO3)2 [CNMNC approved formula]

Named Originally a hypothetical mineral named by Henry Stevens Washington [1867-1934] in 1903. First used to name natural material in 1935 by Norman L. Bowen. For FERROus iron and SILicon in the composition; originally a "normative" mineral in rocks.

IMA status : Renamed IMA Approved; 1988 ()
CLASSIFICATION 
Dana
(8th edition) :
65.01.02.02  
  (65) Inosilicate Single-Width Unbranched Chains, W=1
  (65.01) with chains P=2
  (65.01.02) Orthopyroxenes
  
Nickel-Strunz
(10th edition) :
09.DA.05
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DA) with 2-periodic single chains, Si2O6; pyroxene family
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 18.43 Ǻ, b = 9.080 Ǻ, c = 5.238 Ǻ
Crystal Habit: As coarse anhedral to subhedral grains, up to 5 mm.
Twinning: On {100}
  
Color: Dark green, Dark brown to black
Diaphaneity: Transparent, Translucent
Luster: Vitreous, Sub-Vitreous, Greasy
Hardness (Mohs): 5 to 6
Measured Density: 3.96 g/cm3
Cleavage: 4; {210} and {210} good, {100} and {010} partings
Tenacity: Brittle
Streak: Pale gray brown
  
Polymorphism and Series: Dimorphous with clinoferrosilite. Forms a series with enstatite.
Geologic Setting: In medium- to high-grade metamorphosed iron formations.
Mineral Association: Magnetite, hematite, ferroan diopside, quartz, almandine
  
Synonyms/varieties: Orhoferrosilite, hypersthene
Other Properties: Gemstone Unlikely Available.

 

Ferrosilite
Origin: Summit Rock, Diamond Lake, Douglas Co., Oregon, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Ferrosilite
Origin: Summit Rock, Diamond Lake, Douglas Co., Oregon, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Ferrosilite
Greenish-brown coating on matrix
Origin: Hanksville, Utah, U.SA.
Sample size: 2.5 x 4 cm
Photo: Diederik Visser

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