sedimentary
Sandstone (Ferruginous)
Ferruginous Sandstone (SiO2 with Fe2O3/FeO(OH) cement)
Hardness: 6-7 (Mohs); Color: Reddish-brown, tan, or ochre; Luster: Dull to earthy; Structure: Granular/clastic; Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs)
- Color
- Reddish-brown, tan, or ochre
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Reddish-brown, tan, or ochre; Luster: Dull to earthy; Structure: Granular/clastic; Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and litification of sand-sized mineral grains or rock fragments. The reddish hue indicates iron oxide cementation. These often form in river beds, deserts, or marine environments across various geological ages from Precambrian to Cenozoic.
Uses & applications
Used primarily in construction as a building material, paving, or crushed stone for road base. Historically significant for making grindstones and architecture.
Geological facts
Sandstone accounts for roughly 20-25% of all sedimentary rocks on Earth. The distinct coloring in this specimen is due to hematite or goethite acting as a natural glue between the sand grains.
Field identification & locations
Identify in the field by its 'sandpaper' texture and visible bedding or grain structure. Commonly found in eroded canyons, plateaus, and dry riverbeds globally.
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