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. |
Origin: Cedar City, Iron Co., Utah, U.S.A.Owner: Milton Speckels
Sample size: about 4 cm
Photo and Owner: Milton Speckels
Origin: Delaware County, Pennsylvania, U.S.A.Sample size: 9 x 6.8 x 2.7 cm
Photo: John Veevaert, Trinity Mineral Co
(zoom-in of above)
"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