Identifying Rocks and Minerals/Properties used to identify

The following properties are very useful for identification purposes for minerals use only! For a rock where a suitiblely-sized portion of a suspected mineral can be accessed for testing you may measure mineral properties but don't be tempted to apply them to the rock as a whole. Rocks as in petrology vs mineralogy follow a different set of related but different observations

(Note a principle of analysis is to always use a freshly broken surface to avoid ambiguous findings such as weathering and alterations):

  • Hardness
  • Cleavage
  • Luster
  • Color
  • Streak rock powder
  • Fracture
  • Misc test such as "crystal habit" magnetisim, effervescence, ( acid reaction) radiactivity, ultraviolet response(UV) ductility, tenacity and specific gravity-- (also referred to as "heft" in the field).

In rock characacterization there are also these categories each with specific petrographical descriptors.

  • Texture
  • Structure
  • Fabric
  • Composition

These are described in detail later

You will need a few tools for measuring various aspects of rocks. Not all of them are required, but the more of them that are available to you, the more successful you will be in identifying specimens.

  • Specific Gravity apparatus
  • streak plate-- unglazed back of a porcelain tile for determining "streak" color
  • Magnifying glass
  • Hardness kit (you can use the following as a hardness kit as explained later.)
    • Fingernail
    • Copper penny
    • Knife blade
    • Window glass
    • Steel file

Note a cautionary tale. As technology in materials advanced softness multiplied. A "nail" today may no longer be what iron nails were in Moh's day. Likewise, pennies in the US are no longer copper. In fact metals are measured in Rockwell Hardbess. You can find cross referenced hardness tables on the internet

Types of Rocks · Hardness