Anthophyllite
The name anthophyllite comes from the Latin word anthophyllum, which means “clove”—a reference to the mineral’s clove-brown to dark brown color. Specimens can also be pale green, gray, or white. Anthophyllite is usually found in columnar to fibrous masses. Single crystals are uncommon; when found, they are prismatic and usually unterminated. The iron and magnesium content in anthophyllite is variable. The mineral is called ferroanthophyllite when it is iron-rich, sodium-anthophyllite when sodium is present, and magnesioanthophyllite when magnesium is dominant. Titanium and manganese may also be present in the anthophyllite structure. Anthophyllite forms by the regional metamorphism of iron- and magnesium-rich rocks, especially silica-poor igneous rocks. It is an important component of some gneisses and crystalline schists and is found worldwide. Anthophyllite is one of several minerals referred to as asbestos.
Name: From the Latin anthophyllum, meaning clove, in allusion to the mineral’s color.
Association: Cordierite, talc, chlorite, sillimanite, mica, olivine, \hornblende,” gedrite, magnesio-cummingtonite, garnet, staurolite, plagioclase.
Polymorphism & Series: Forms a series with magnesio-anthophyllite and ferro-anthophyllite.
Mineral Group: Amphibole (Fe{Mn{Mg) group: 0.1 Mg=(Mg + Fe 2+) 0.89; (Ca + Na)B < 1.34; Li < 1.0; Si ¸ 7.0.
Anthophyllite from Bastnäs mines, Riddarhyttan, Västmanland
Anthophyllite from New England quarry, Yealmpton, Devon
Anthophyllite from Wissahickon Creek, Fairmount Park, Philadelphia, Pennsylvania
Antofillit-(Anthophyllite)-Mineral
Contents
- Chemical Properties of Anthophyllite
- Physical Properties of Anthophyllite
- Optical Properties of Anthophyllite
- Occurrence
- Distribution
- References
Chemical Properties of Anthophyllite
| Chemical Classification | Inosilicates |
| Chemical Composition | (Mg,Fe)7Si8O22(OH)2 |
Physical Properties of Anthophyllite
| Color | White, greenish grey, green, clove brown, or brownish gree |
| Streak | White to greyish-white. |
| Luster | Vitreous, Pearly |
| Cleavage | Perfect Perfect on {210}, imperfect on {010}, {100} |
| Diaphaneity | Transparent, Translucent |
| Mohs Hardness | 5½ – 6 on Mohs scale |
| Tenacity | Brittle; elastic when fibrous |
| Diagnostic Properties | Characterized by clove brown color, but unless in crystals, difficult to distinguish from other amphiboles without optical and/or X-ray tests |
| Crystal System | Orthorhombic |
| Fracture | Conchoidal |
| Density | 2.85 – 3.57 g/cm3 (Measured) 3.67 g/cm3 (Calculated) |
Optical Properties of Anthophyllite
Anthophyllite in thin section
| Optic Sign | Biaxial (+) |
| Birefringence | δ = 0.017 – 0.023 |
| Relief | Moderate |
| 2V: | Measured: 57° to 90°, Calculated: 82° to 90° |
| Dispersion | r > v or r < v |
Occurrence
From medium- or high-grade metamorphism, in amphibolites, gneisses, metaquartzites, iron formations, granulites, and schists derived from argillaceous sediments, ultrama¯c, or ma¯c igneous rocks; a retrograde reaction product.
Distribution
From Kongsberg and Snarum, Norway. At Schneeberg, Saxony, Germany. From Norberg, Sweden. At He·rmanov, Czech Republic. In Greenland, from Fisken½sset. In the USA, from Chester¯eld, Hampshire Co., Massachusetts; the Carleton talc mine, near Chester, Windsor Co., Vermont; near Media, Delaware Co., Pennsylvania; the Day Book deposit, near Spruce Pine, Mitchell Co., North Carolina; in California, at the Winchester quarry, Riverside Co., and near Co®ee Creek, Carrville, Trinity Co.; in the Copper Queen mine, Prairie Divide, Park Co., Colorado. From Munglinup, Western Australia.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
Mindat.org. (2019). Anthophyllite: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
