sedimentary
Sandstone (Greywacke)
Arenite / Wacke (SiO2 + varied clasts)
Hardness: 6-7 (Mohs); Color: Grey, tan, or salt-and-pepper; Luster: Dull/Earthy; Structure: Clastic, fine to medium-grained; Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs)
- Color
- Grey, tan, or salt-and-pepper
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Grey, tan, or salt-and-pepper; Luster: Dull/Earthy; Structure: Clastic, fine to medium-grained; Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. This specimen appears to be a lithic sandstone or greywacke formed in a marine environment where tectonic activity contributes poorly sorted sediment.
Uses & applications
Used extensively in construction as a building stone (dimension stone), road base, and as an abrasive in some industrial processes. It is also a key reservoir rock for petroleum and water.
Geological facts
Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The famous monuments at Petra, Jordan, are carved entirely out of sandstone cliffs. This specific grey variety is often associated with ancient turbidite deposits.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and visible grains. Often found in coastal regions, riverbeds, and mountainous uplift areas. Collectors look for unique banding or fossil inclusions.
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