Adding Ti and Fe to corundum produces the blue of sapphire . Olivine , pyroxene , and amphibole get deeper colors with increasing Fe content. Mineral Classification Minerals may be classified by the type of anion or anionic group they contain or by their crystal structure. Silicate minerals most abundant in Earth's crust and mantle. Si atom surrounded by four oxygens.
Ratio decreases as more O is shared and mineral becomes more interlinked.
The manner in which silicon is bonded in a mineral is also used for classification. Al replaces Si in the tetrahedra. Not an important test in minerals lacking metallic luster. Luster is largely controlled by the type of bonding in the mineral. Vitreous and pearly luster are the most common nonmetallic lusters.