ABSTRACT
A mineral is a homogeneous, naturally occurring inorganic substance with an orderly atomic structure. This chapter talks about five mineral properties. They are: color, streak, luster, transparency and cleavage. Most minerals readers see while walking around an outcrop or a road cut reflect the local geology. The chapter also talks about six crystal systems: isometric, tetragonal, hexagonal, orthorhombic, monoclinic and triclinic. Minerals do not have to be crystalline, but they must be capable of being crystals. A quartz crystal has a distinct hexagonal shape because the crystal lattice has that shape. Some minerals, such as quartz, can have more than one crystal form depending on the temperature and pressure of formation. Many fine mineral and crystal specimens come from rock cavities where they were able to grow uninterrupted. Some crystals produce an electrical charge when compressed, making them useful in precision instruments.
