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Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds
From the Old English term col, which has meant mineral of fossilized carbon since the 13th century
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Greenschist is a metamorphic rock that is formed under lowest temperatures and pressures and is usually produced by regional metamorphism
From minerals such as chlorite, serpentine, and epidote, and platy minerals such as muscovite and platy serpentine which are green in color
Durable Rock, Medium Hardness Rock
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock