| This rock is a dark gray schistose rock containing radiating aggregates of cummingtonite and occasionally pyrrhotite. |
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| The two minerals can have similar distinctive brown colors and are hard to differentiate from each other, although cummingtonite is typically darker and slightly denser. |
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| Accessory chlorite, magnetite or ilmenite, titanite, apatite, partly chloritized biotite, epidote, pyrite and sometimes cummingtonite, are present. |
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| Magnesium-rich amphiboles such as anthophyllite, cummingtonite, and tremolite are colourless or light in colour. |
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| Gedrite and cummingtonite coexist with garnet in rocks enriched in aluminum and iron. |
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| Rocks containing cummingtonite or grunerite are characteristic of metamorphosed iron formations associated with iron oxides, iron-rich sheet silicates, carbonates, and quartz. |
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