Sandstone (with Iron concretions/staining)

Physical Properties

Hardness: 6-7 (individual grains); Color: Tan, yellow-orange, and reddish-brown; Luster: Dull/Earthy; Crystal Structure: Clastic (usually granular texture); Cleavage: None; Specific Gravity: 2.2 to 2.8

Formation & Geological History

Formed through the accumulation and compaction of mineral particles or rock fragments (detritus) in desert, river, or ocean floor environments. This specific piece shows significant iron oxidation (limonite/hematite staining) which occurred as groundwater flowed through the porous rock.

Uses & Applications

Commonly used as a building material, in the glass industry (if high silica content), and as an aquifer for groundwater or reservoir for oil and gas.

Geological Facts

Sandstone accounts for about 20% of all sedimentary rocks on Earth. The 'red beds' seen in the Grand Canyon are classic examples of iron-rich sandstone similar in chemistry to this specimen.

Field Identification & Locations

Identify by its gritty texture (feels like sandpaper) and lack of distinct crystals visible to the naked eye. Often found in layers (strata). To identify in the field, look for cross-bedding or ripple marks indicative of ancient water or wind movement.

Identified on: 4/15/2026

Mode: Standard