Minerals

mineral / chemical formula	properties / significance	occurrence
magnetite (lodestone)Fe2O3	black ferrimagnetic mineral in the spinel group, converts to hematite on oxidation, produced from peridotites and dunites by serpentinization.	most igneous rocks and metamorphic rocks, many sedimentary rocks, widespread ore deposits, banded iron formations
quartz (silica) SiO2 [gallery, 2, 3]	silica tetrahedra, tectosilicate, hexagonal rhombohedral crystals in numerous varieties named for color and microstructure, numerous growth forms	commonest mineral, igneous, sedimentary, and metamorphic rocks, hydrothermal veins and pegmatites, granite, sandstone, limestone