sedimentary
Ferruginous Sandstone (with ripple marks)
Arenite with Iron-Oxide (Fe2O3) cement
Hardness: 6-7 (Mohs scale); Color: Brown, reddish-tan, or mahogany; Luster: Dull/Earthy; Crystal structure: Clastic (sand-sized grains); Cleavage: None; Specific gravity: 2.3-2.6
- Hardness
- 6-7 (Mohs scale)
- Color
- Brown, reddish-tan, or mahogany
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Brown, reddish-tan, or mahogany; Luster: Dull/Earthy; Crystal structure: Clastic (sand-sized grains); Cleavage: None; Specific gravity: 2.3-2.6
Formation & geological history
Formed through the accumulation and litification of sand-sized quartz grains in high-energy environments like rivers or beaches. The iron oxide (cementing agent) typically dates from the Mesozoic or Paleozoic eras, often in arid or oxidizing conditions.
Uses & applications
Used primarily in construction as a building stone or road aggregate. Specimens with distinct ripple marks are valued for geological teaching and small-scale fossil/rock collecting.
Geological facts
This specimen displays 'fossilized' ripple marks, which are sedimentary structures indicating the direction of ancient water currents or wind flow at the time of deposition million of years ago.
Field identification & locations
Identify in the field by its gritty 'sandpaper' texture and visible parallel ridges (ripple marks). Commonly found in the Southwest United States (e.g., Grand Canyon formations) and coastal sandstone cliffs.
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