Some minerals may be colored by minor impurities or minute inclusions. The lab manuals give some examples of minerals with different luster. The hardness of minerals is a useful property as long as tests are made by scratching, rather than crushing, one mineral against another. It is difficult to test for hardness of fine-grained aggregates unless you are sure you are testing a single grain and not breaking grains off. The lab manuals and mineralogy textbooks in the lab describe how to use this classification system.
Cleavage is one of the most useful properties for identifying common minerals.
Look at the atomic model of flourite and calcite and then study the cleaved fragments of these minerals under the binocular microscope. Note how for a given mineral, each fragment shows the same cleavage planes and angles. Its irregular pattern of breaking is called conchoidal fracture. This lack of cleavage is often very useful in identifying quartz. Feldspars are an important group of silicates and the most common minerals in the crust of the earth.