What is a mineral of pale steel-gray color and metallic luster, occurring in isometric crystals, and also massive. It is a sulphide of cobalt containing some nickel or copper called?

linnaeite — A mineral of pale steel-gray color and metallic luster, occurring in isometric crystals, and also massive. It is a sulphide of cobalt containing some nickel or copper. (Webster's 1913.)

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