lode

In geology and mining, a lode (also lode deposit) is a natural concentration of ore that fills a fracture, fault, or sheet-like zone within host rock. Lodes are typically formed by hydrothermal fluids that precipitate ore minerals as they move through cracks, resulting in a coherent solid body of ore that can extend over meters to many kilometers. The term is commonly used for hard rock deposits, especially gold-bearing lodes, as distinct from alluvial or placer deposits.

Most lodes contain ore minerals such as native gold, gold-bearing sulfides (arsenopyrite, pyrite), sphalerite, galena, chalcopyrite, or magnetite, embedded in gangue minerals like quartz or carbonate. They may occur as tabular masses, veins with narrow width, or as extensive ore bodies that occupy large fractures. Lodes can be continuous or segmented by faults, and ore grade often varies with structure and depth.

An ore vein is a narrower, sheetlike projection within a lode, whereas a lode refers to the broader, primary ore body that can contain multiple veins. Lode deposits are typically exploited by underground mining methods (drift, stope, cut-and-fill) or by block caving in large, low-grade bodies. In contrast, placer deposits accumulate free, weathered particles near the surface and are mined by surface methods.

Prominent lode gold deposits include the Carlin Trend in Nevada and the Homestake mine in South Dakota. Lode deposits underpin many metal-producing regions and require detailed geological mapping, drilling, and ore-control techniques to establish mineable ore reserves and optimize ore recovery.