The minerals that form as magma cools are known as silicates because of their high proportion of silicon and oxygen. Silicon is at the center of the tetrahedron and oxygen at the corners. Silicate minerals are classified by the degree of linkage between tetrahedra. Silicon can make 4 bonds, Oxygen 2 bonds. The Fe and Mg are the charge-balancing cations.
Rocks are aggregates of minerals and mineraloids.
Such specimens are not as common as rocks, which are mixtures of more than one type of mineral. In this lab your objective is to be able to recognize these rock-forming minerals in hand specimens. The minerals that form as magma cools are known as silicates because of their high proportion of silicon and oxygen. Silicon is at the center of the tetrahedron and oxygen at the corners. Representations of silicate tetrahedra.