sedimentary
Sandstone (Red Flagstone)
Clastic sedimentary rock (primarily Quartz - SiO2)
Hardness: 6-7 on Mohs scale (grains); Color: Pink to Red due to iron oxide (hematite); Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific gravity: 2.2-2.8.
- Hardness
- 6-7 on Mohs scale (grains)
- Color
- Pink to Red due to iron oxide (hematite)
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale (grains); Color: Pink to Red due to iron oxide (hematite); Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific gravity: 2.2-2.8.
Formation & geological history
Formed from the lithification of sand-sized mineral particles or rock fragments through compaction and cementation. Often associated with ancient river deltas, beaches, or desert sand dunes. This specific coloring often originates from the Permian or Triassic periods (approx. 200-300 million years ago).
Uses & applications
Primary use is in construction as flagstone for paving, walkways, and patios. Historically used for architectural facades and grinding stones. Occasionally used for small rock-cairn landscaping and indoor decorative hearths.
Geological facts
Red sandstone is what gives the famous landscapes of the American Southwest (like the Grand Canyon and Zion National Park) their iconic color. The color is essentially 'rusting' on a geological scale, as iron-rich minerals oxidize over millions of years.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and distinct layering (bedding). It can often be easily split into thin plates along bedding planes. Found globally, but specifically abundant in the United Kingdom, Southwest USA, and India.
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