sedimentary
Sandstone (Ferruginous)
Arenite (composed primarily of SiO2 with iron oxide Fe2O3 cement)
Hardness: 6-7 (Mohs/Quartz grains); Color: Brown, reddish-tan, or rusty; Luster: Dull/Earthy; Structure: Clastic, fine-to-medium grained; Specific Gravity: 2.2–2.6.
- Hardness
- 6-7 (Mohs/Quartz grains)
- Color
- Brown, reddish-tan, or rusty
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs/Quartz grains); Color: Brown, reddish-tan, or rusty; Luster: Dull/Earthy; Structure: Clastic, fine-to-medium grained; Specific Gravity: 2.2–2.6.
Formation & geological history
Formed through the accumulation, compaction, and lithification of sand-sized mineral grains. This specific specimen exhibits iron-oxide staining, suggesting formation in an environment with oxygenated groundwater or subaerial weathering.
Uses & applications
Commonly used as a building stone (dimension stone), in glass manufacturing if pure silica, or as a source of aggregate for construction and road paving.
Geological facts
Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The reddish-brown color specifically indicates the presence of hematite or limonite acting as a cementing agent between the quartz grains.
Field identification & locations
Identify in the field by its gritty 'sandpaper' feel and visible grains. These are commonly found in riverbeds, desert dunes, and coastal environments. This specimen appears water-worn and rounded, likely sourced from a stream or glacial till.
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