Mineral Information and Data:

Anthophyllite
[]Mg7Si8O22(OH)2 [CNMNC approved formula]

Named in 1861 from the neo-Latin for clove (for its color).

IMA status : Redefined IMA Approved; 1978 ()
CLASSIFICATION 
Dana
(8th edition) :
66.01.02.02  
  (66) Inosilicate Double-Width Unbranched Chains, W=2
  (66.01) with P=2 amphibole configuration
  (66.01.02)
  
Nickel-Strunz
(10th edition) :
09.DE.05
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DE) with 2-periodic double chains, Si4O11; Clinoamphiboles
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 18.54 Å, b = 18.03 Å, c = 5.28 Å
Crystal Habit: Crystals prismatic, rare; massive, fibrous, or lamellar
  
Color: White, grey, greenish, brownish green, clove-brown, dark
Diaphaneity: Transparent to translucent
Luster: Vitreous, pearly on cleavage
Hardness (Mohs): 5.5 to 6
Measured Density: 2.9 to 3 g/cm3
Cleavage: 3; {210} perfect, {010} and {100} imperfect
Tenacity: Brittle, fibres are elastic
Streak: Colorless or greyish
  
Geologic Setting: From medium- or high-grade metamorphism, in amphibolites, gneisses,
metaquartzites, iron formations, granulites, and schists derived from argillaceous sediments,ultramafic, or mafic igneous rocks; a retrograde reaction product
Mineral Association: Cordierite, talc, chlorite, sillimanite, mica, olivine, hornblende, gedrite,
magnesio-cummingtonite, garnet, staurolite, plagioclase
  
Synonyms/varieties: Anthogrammite, antholite, anthophylline, schillerspath, strelite, thalackerite (metallic luster var.), picroamosite (Fe3+ rich var.), valleite
Other Properties: Gemstone Unlikely Available.
Comments: Series with magnesio-anthophyllite and ferro-anthophyllite. Member of amphibole group.

 

Anthophyllite
Origin: Cedar City, Iron Co., Utah, U.S.A.
Owner: Milton Speckels
Sample size: about 4 cm
Photo and Owner: Milton Speckels

 

Anthophyllite
Origin: Delaware County, Pennsylvania, U.S.A.
Sample size: 9 x 6.8 x 2.7 cm
Photo: John Veevaert, Trinity Mineral Co

 

Anthophyllite
(zoom-in of above)

 

Anthophyllite
"Hermanov Balls", These are cut nodules with a fibrous radiating outer rim consisting of anthophyllite, an inner talc rim (not always present) and a flattened phlogopite core. The outer rim is coated with more phlogopite.
Origin: Hermanov, Moravia, Czech Republic
Photo: Diederik Visser
Sample size: 5 x 5 cm

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