Grunerite

Grunerite is a mineral of the amphibole group of minerals with formula Fe7Si8O22(OH)2. It is the iron endmember of the grunerite-cummingtonite series. It forms as fibrous, columnar or massive aggregates of crystals. The crystals are monoclinic prismatic. The luster is glassy to pearly with colors ranging from green, brown to dark grey. The Mohs ha...
Found on http://en.wikipedia.org/wiki/Grunerite

grunerite

(from the article `olivine`) ...four-component) system Fe2O3-FeO-SiO2-H2O, fayalite is associated with the minerals greenalite (iron-serpentine), minnesotaite (iron-talc), and ... ...to about Fe2Mg5Si8O22(OH)2 is represented by the orthorhombic amphibole known as anthophyllite. The monoclinic cummingtonite-grunerite series ... [2 rel...
Found on http://www.britannica.com/eb/a-z/g/76
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