Hypothermal deposits form at high temperatures (300–600°C) and high pressures at great crustal depths (typically >3 km). They include high-temperature gold-quartz veins, pegmatites, and contact metasomatic (skarn) deposits. They are distinguished from mesothermal (200–300°C), epithermal (50–200°C, shallow), and telethermal deposits by their depth and temperature of formation — Lindgren's classification system.