Minerals are the basic components of rocks and the most common visible substances on Earth. You are probably most familiar with minerals as the beautiful gemstones in jewelry or as masses of natural crystals displayed in museums. What you may not realize is that minerals are also the natural materials from which every inorganic (not composed of any plant or animal matter) item in our industrialized society has been manufactured. For example, the pencil you write with was made with several minerals (see figure). The walls in your home are likely made with a mineral called gypsum, the glass with quartz, and the pipes with copper (see display cabinet 59 in McGilvrey hallway directly outside the lab room).
There are more than 3000 different minerals! A mineral by definition must be:
Element Volume proportion
Because they are so important geologists sometimes refer to these elements as the BIG 8. They are easy to remember if you make a mnemonic like the following: Only strong athletes in college study past midnight. (Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium).
Elements combine to form minerals (Si and O combine to form quartz). Minerals combine to form rocks (quartz and feldspar combine to form granite).
KSU's Geology Department offers an entire course on the study of minerals (Mineralogy) but for this lab we will focus on 10-12 rock forming minerals and the physical properties used to identify them. Display cabinet 64 in the hallway shows many of the physical mineral properties including color, streak (its appearance in powdered form), hardness (resistance to being scratched), luster (its appearance in reflected light), cleavage (tendency to break along certain planes), and density.
For instance, hardness is one of the more useful identifying properties for a mineral. Geologist's have a scale (the Moh's hardness scale) which ranks some common minerals from 1 to 10:
Again, can you think of a funny mnemonic to help you remember the Moh's hardness scale? (write it here for future reference).
You can see examples of various minerals at The Mineral Gallery Web Site: view minerals by type.
Commonly, isolated mineral specimens look very different from how they appear in rocks. For this reason we will also show you what minerals look like in rocks during this lab. There are only three types of rocks: