An ore deposit is a naturally occurring concentration of one or more minerals or metals within the Earth's crust that is, or potentially could be, extracted at a profit. Deposits form through a wide range of geological processes including magmatic crystallization, hydrothermal fluid circulation, sedimentary accumulation, and chemical or mechanical weathering. Bauxite deposits typically form as residual laterite blankets through intense tropical weathering of aluminum-rich parent rocks, concentrating aluminum hydroxide minerals near the surface. Gold deposits arise from diverse processes, including orogenic hydrothermal veins formed during mountain-building events, epithermal systems associated with volcanic activity, and placer deposits where weathering and water transport concentrate gold mechanically in river or beach sediments. Iron ore deposits commonly originate as banded iron formations deposited in ancient oceans, later enriched through supergene weathering, or as magmatic and skarn-related magnetite bodies. Diamond deposits form deep in the mantle under extreme pressure and temperature, then are transported to the surface by kimberlite or lamproite volcanic pipes, with secondary alluvial and marine placer deposits forming where erosion redistributes diamonds from primary sources.
