Petrology has three subdivisions&colon; igneous, metamorphic, and sedimentary petrology. Apatite is most commonly found in sedimentary, metamorphic, igneous, and volcanic rocks. The Central Cordillera is a mountain range of sedimentary, metamorphic and igneous rocks. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rocks. Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Small grains of magnetite occur in almost all igneous and metamorphic rocks. Ilmenite is a common accessory mineral found in metamorphic and igneous rocks. Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. A variety of igneous and metamorphic rock supports Grass Valley. Sparta is in the Highlands which is composed of igneous and metamorphic rock. These concepts are also applicable to metamorphic and sedimentary petrology. It is a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Quarrying of the igneous and metamorphic rocks has also been a significant industry. Grinding stones were made of quartzite, granitic, or metamorphic rock. They can also be metamorphic or igneous.