Classifying minerals can range from simple to very difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex chemical or X-ray diffraction analysis; these methods, however, can be costly, time-consuming, and even risk damaging the sample. Physical properties commonly used are:

  1. Crystal structure and habit: A mineral may show good crystal habit or form, or it may be massive, granular or compact with only microscopically visible crystals.
  2. Hardness: the physical hardness of a mineral is usually measured according to the Mohs scale that goes from 1 to 10. Minerals with a given Mohs hardness can scratch the surface of any mineral that has a lower hardness than itself. The minerals that define the scale are talc 2- gypsum 3- calcite 4- fluorite 5- apatite 6- orthoclase feldspar 7- quartz 8- topaz 9- corundum 10- diamond
  3. Luster indicates the way a mineral's surface interacts with light and can range from dull to glassy (vitreous).
  4. Metallic -high reflectivity like metal, e.g. galena
  5. Sub-metallic -slightly less than metallic reflectivity, e.g. magnetite
  6. Vitreous -the luster of a broken glass, e.g. quartz
  7. Pearly -a very soft light shown by some layer silicates, e.g. talc
  8. Silky -a soft light shown by fibrous materials, e.g. gypsum
  9. Dull/earthy -shown by finely crystallized minerals, e.g. the kidney ore variety of hematite
  10. Color indicates the appearance of the mineral in reflected light or transmitted light for translucent minerals (i.e. what it looks like to the naked eye).
  11. Streak refers to the color of the powder a mineral leaves after rubbing it on an unglazed porcelain streak plate.
  12. Cleavage describes the way a mineral may split apart along various planes. In thin section, cleavage is visible as thin parallel lines across a mineral.
  13. Fracture describes how a mineral breaks when broken contrary to its natural cleavage planes, e.g. a chonchoidal fracture is a smooth fracture with concentric ridges of the type shown by glass.
  14. Specific gravity relates the mineral mass to the mass of an equal volume of water, namely the density of the material. While most minerals, including all the rock-forming minerals, have a specific gravity of 2.5 - 3.5, a few are noticeably more or less dense, e.g. several sulphide minerals have high specific gravity compared to the common rock-forming minerals.
  15. Other properties: fluorescence (response to ultraviolet light), magnetism, radioactivity, tenacity (response to mechanical induced changes of shape or form), and reactivity to dilute acids.