
sedimentary
Weathered sandstone boulder
Sandstone, chiefly quartz (SiO₂) with feldspar and iron-oxide cement
AI-generated identification · may be incorrectTypically Mohs hardness 6–7, tan to gray-brown, dull to slightly gritty, and composed of visible sand-sized grains; it may show bedding, pores, and iron staining. The photograph is low-resolution, so exact mineralogy and texture cannot be confirmed.
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Physical properties
Typically Mohs hardness 6–7, tan to gray-brown, dull to slightly gritty, and composed of visible sand-sized grains; it may show bedding, pores, and iron staining. The photograph is low-resolution, so exact mineralogy and texture cannot be confirmed.
Formation & geological history
Formed when sand was deposited, compacted, and cemented in ancient rivers, beaches, dunes, or shallow seas; age cannot be determined from the image. Weathering has rounded the exposed surface and darkened portions with biological or mineral staining.
Uses & applications
Commonly used as building stone, paving, landscaping rock, aggregate, and occasionally sculpture material. This ordinary outdoor boulder has little jewelry or collector value.
Geological facts
Sandstone strength and color depend strongly on cement type: silica makes it durable, while clay or calcite cement makes it softer and more weatherable. The dark surface may be lichen, soil, or weathering rather than a distinct mineral.
Field identification & locations
Look for gritty texture, sand-sized grains, layered bedding, and scratching resistance greater than steel with quartz-rich varieties; acid testing can distinguish calcareous sandstone. Common worldwide, especially in sedimentary basins and glaciated areas.
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