The physical properties of a mineral helps in its classification. At times it is easy and at times difficult. Some of the common physical properties used are its hardness. This hardness is measured by a Moh’s scale. Next is the crystal structure and habit. Some minerals display good structure and habit, or they may be massive, or granular or ‘compact with only microscopically visible crystals’. The other common physical properties are its luster, color, streak, cleavage, fracture, density, specific gravity, fluorescence, radioactivity and magnetism. Each is a study on its own, and is not so simple as it seems.