1. a porous, friable rock formed by the precipitation of calcium carbonate from water, typically found in hot spring deposits or tufa formations
Usage: geology; also spelled calc-tuff

Examples

• The geologist examined the calctuff deposits near the thermal spring.
• Calctuff formations often contain fossils of plants and small organisms.
• The porous nature of calctuff makes it useful as a building material in some regions.
• Ancient calctuff layers provide evidence of past geothermal activity.