Definition of penninite
: a mineral approximately (Mg,Fe,Al)6(Si,Al)4O11(OH)8 of the chlorite group consisting of a basic aluminosilicate of magnesium, iron, and aluminum, that is monoclinic and is commonly emerald or olive green (hardness 2.–2.5, specific gravity 2.6–2.85)
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Origin and Etymology of penninite
penninite from German pennin (from Pennine Alps) + English -ite; pennine from German pennin
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