1. A hard, fine-grained igneous rock formed by the alteration of granite, typically containing quartz and mica, and often associated with tin and tungsten ore deposits.
Usage: geology; technical

Examples

• The miners discovered greisen veins running through the granite bedrock.
• Greisen formations are commonly found in areas with tin deposits.
• Geologists study greisen to understand the hydrothermal alteration of granitic rocks.
• The greisen in this region contains valuable tungsten ore.