sedimentary
Sandstone Pebble with Mineral Encrustation
Quartz Sandstone with Calcite/Halite Crust
Hardness: 6-7 (base rock, quartz), 3 (crust, calcite). Color: Greyish-brown host rock with pinkish-white encrustation. Luster: Dull to earthy on rock surface, vitreous/crusty on deposit. Grain size: Fine to medium-grained.
- Hardness
- 6-7 (base rock, quartz), 3 (crust, calcite)
- Color
- Greyish-brown host rock with pinkish-white encrustation
- Luster
- Dull to earthy on rock surface, vitreous/crusty on deposit
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Physical properties
Hardness: 6-7 (base rock, quartz), 3 (crust, calcite). Color: Greyish-brown host rock with pinkish-white encrustation. Luster: Dull to earthy on rock surface, vitreous/crusty on deposit. Grain size: Fine to medium-grained.
Formation & geological history
Formed by the accumulation, compaction, and cementation of sand-sized grains, primarily quartz. The rounded shape indicates erosion by water along a riverbed or coastline, while the superficial pinkish-white crust formed via secondary mineral precipitation or encrusting organism remains (like calcareous algae or salt crusts).
Uses & applications
Commonly used as river rock for landscaping, decorative gardens, aggregate in concrete, or educational geological specimens.
Geological facts
River pebble shapes are smoothed by natural abrasive action over hundreds or thousands of years. The distinctive crust pattern often occurs when saline or calcium-rich water evaporates on the rock surface.
Field identification & locations
Identified by its rounded pebble shape, sandy gritty surface texture, and thin, flakey superficial mineral crust that reacts or scrapes off easily. Found worldwide along beaches, rivers, and glacial till deposits.
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