Knowra Pegmatite Pegmatite Pegmatite is an exceptionally coarse-grained igneous rock, usually granitic, whose crystals can grow to unusually large sizes. It commonly forms in the final stages of magma crystallization.
Fractional crystallization : The separation of crystals from magma as they form, changing the composition of the remaining melt. This process concentrates water and rare elements in residual melts that can form pegmatite.
Granite : A coarse-grained igneous rock composed mainly of quartz and feldspar. Most pegmatites have granitic compositions, though their crystals are far larger.
Lithium : A soft, lightweight alkali metal used in batteries, ceramics, and other technologies. Some pegmatites are mined for lithium-bearing minerals such as spodumene.
Black Hills pegmatites : A group of pegmatite bodies in South Dakota known for lithium, tantalum, and other minerals. Their deposits illustrate the economic importance of rare-element pegmatites.
Pegmatite formation : The geological processes that produce pegmatite bodies and their exceptionally coarse crystals. Its mechanisms remain debated, especially the roles of melt, fluids, and rapid growth.
Volatile components : Substances such as water and fluorine that readily enter a gas phase under geological conditions. Volatiles lower melt viscosity and affect how pegmatite crystallizes.
Quartz : A common mineral composed of silicon dioxide, with a hardness of seven on the Mohs scale. Quartz is a frequent constituent of granitic pegmatites.
Spodumene : A lithium-bearing pyroxene mineral found in some granitic pegmatites. It is a principal lithium ore in economically important pegmatite deposits.
Pala pegmatite district : A gem-producing pegmatite district in San Diego County, California. Its mines are known for tourmaline and other gem minerals crystallized in pegmatites.
Magma : Molten or partly molten rock beneath Earth’s surface, including dissolved gases and suspended crystals. Pegmatite models must explain how magma evolves into its unusual final-stage melts.
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