For additional sedimentary rock related items, click here . It includes 6 minerals and 6 each of the three types of rock - igneous, metamorphic and sedimentary. Minerals are chemical compounds or elements found naturally in the crust of the earth. Some minerals have a fixed chemical composition, while others are a series of related compounds. Rocks are usually portions of large masses of material that make up the earth's crust.
Most rocks contain several minerals.
The key also includes a useful and interesting fact about a geologic feature found in each state. The removable specimens come in a nice display tray. This collection offers an exciting look at some of the most peculiar physical properties exhibited by minerals. Properties illustrated include double refraction, magnetism, taste, fluoresc ence, thermal expansion and conductivity. Cleavage Collection - Cleavage is the tendency of minerals to break along preferred directions.