How to Identify Black Minerals ThoughtCo
Jul 29, 2019· Magnetite (or lodestone) is a common accessory mineral in coarsegrained igneous rocks and metamorphic rocks. It may be grayblack or have a rusty coating. Crystals are common, with striated faces shaped in octedrons or dodecedrons. Look for a black streak and a strong attraction to a magnet. Characteristics: Metallic luster; hardness of 6.