Cummingtonite
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Cummingtonite is a metamorphic amphibole with the chemical composition 25Si8O222, magnesium iron silicate hydroxide.
Amphibole Cummingtonite w chlorite in schist Magnesium iron silicate 3800 foot level Homestake Mine Lawrence C Ounty South Dakota 2071
Fibrous, brownish crystals of cummingtonite – Locality: Dannemora Mine, Uppsala Län, Uppland, Sweden
Grunerite
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Grunerite is a mineral of the amphibole group of minerals with formula Fe7Si8O222. It is the iron endmember of the grunerite-cummingtonite series. It forms as fibrous, columnar or massive aggregates o
Cummingtonite
…where it was discovered in 1824. It is also found in Sweden, South Africa, Scotland, and New Zealand. Cummingtonite is a member of the cummingtonite-grunerite solid solution series which ranges from Mg 7Si 8O 22(OH) 2 for magnesiocummingtonite to the iron rich grunerite endmember Fe 7Si 8O 22(OH) 2. Cummingtonite…
Sprays of small, prismatic grunerite crystals on matrix, field of view 5mm, from Marquette Co., Michigan, US
Scanning electron microscope image of asbestos fibres (grunerite var. amosite)