sedimentary
Sandstone (Ferruginous)
Sandstone (SiO2 with iron oxide inclusions)
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, purple, or tan; Luster: Dull/Earthy with sparkling quartz grains; Crystal structure: Clastic/Granular; Specific Gravity: 2.2–2.8
- Hardness
- 6-7 on Mohs scale
- Color
- Reddish-brown, purple, or tan
- Luster
- Dull/Earthy with sparkling quartz grains
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, purple, or tan; Luster: Dull/Earthy with sparkling quartz grains; Crystal structure: Clastic/Granular; Specific Gravity: 2.2–2.8
Formation & geological history
Formed from the accumulation and cementation of sand-sized mineral grains or rock fragments. The reddish-purple hue suggests the presence of hematite or other iron oxides during the lithification process. Often found in ancient riverbeds or coastal environments.
Uses & applications
Commonly used in construction, as a building stone (brownstone), for paving, and occasionally for decorative landscaping or historical carvings.
Geological facts
Sandstone accounts for roughly 20-25% of all sedimentary rocks. It is highly porous and often acts as a significant aquifer or reservoir for petroleum and natural gas.
Field identification & locations
Identify in the field by its 'sandpaper' texture and visible sparkling grains under direct light. Commonly found in desert regions, canyons, and eroded cliffsides. Collectors look for unique banding or color patterns.
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