sedimentary
Arkosic Sandstone (or Conglomeritic Sandstone fragment)
Arkose (rich in feldspar)
Hardness: 6-7 (Mohs scale); Color: light gray, pinkish, or tan; Luster: earthy/dull; Crystal structure: clastic (granular); Cleavage: none (fractures across grains); Specific gravity: 2.5-2.7
- Hardness
- 6-7 (Mohs scale)
- Color
- light gray, pinkish, or tan
- Luster
- earthy/dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: light gray, pinkish, or tan; Luster: earthy/dull; Crystal structure: clastic (granular); Cleavage: none (fractures across grains); Specific gravity: 2.5-2.7
Formation & geological history
Formed through the rapid weathering and deposition of feldspar-rich igneous or metamorphic rocks (like granite). This specimen appears to be a fragment of a coarse-grained sedimentary rock formed in high-energy environments like riverbeds or alluvial fans.
Uses & applications
Primarily used as a building stone or crushed stone in construction; sometimes used as an indicator for potential petroleum reservoirs in geological exploration.
Geological facts
Arkose signifies that the source rock was not far away and deposition happened quickly, as feldspar usually weathers into clay if transported over long distances.
Field identification & locations
Identify in the field by its 'gritty' feel and the presence of visible pink or cream-colored feldspar grains mixed with quartz. Found commonly in basins near mountain ranges. For collectors, it represents the tectonic history of a region.
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