The in-place granular disintegration product of granite is called

• A. Grus
• B. Quartz sand
• C. Sandstone
• D. Gravel

Answer: (A)

Granite exposed to weathering breaks down mechanically into a loose, gritty, sandy-muddy mass that remains in place at the surface. This in-place granular disintegration product is called grus. It’s the weathered, in-situ material you’d find at the ground surface before further alteration to saprolite or soil or before any transport away as scree or alluvium.

Quartz sand would be isolated quartz grains, not the specific in-place product of granite weathering; sandstone is a cemented sedimentary rock formed from deposited sand grains; gravel consists of larger rock fragments that have been transported and deposited. The term grus uniquely describes the granular, in-situ product of granite weathering.