H 2 O in its liquid or gaseous form. The silicon cation has a charge of plus four - the oxygen anion has a charge of negative 2. This pattern of atoms allows some minerals to have distinctive crystalline form and cleavage. Very importantly, the stacking arrangement of the atoms. One of the most common physical properties is not necessarily the most useful.
Color is obvious, but varies too much.
Luster is the first property we examine to see if the mineral is metallic or nonmetallic - that dictates which identification chart we use. Crystal form and cleavage can be observed immediately and hardness checked almost as quickly. Again, whether a mineral has cleavage or not depends upon the stacking arrangement of the atoms of the mineral. If there is a regular, geometric arrangement of the atoms, then the mineral will manifest a regular shape as a hand sample and will likely possess cleavage. The reason that most rock-forming minerals are silicates is that oxygen and silicon are the two most abundant elements in Earth s crust AND they readily combine to form the silicate molecule.