sedimentary

Banded Sandstone

Arenite (composed primarily of Quartz: SiO2)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Reddish-brown, tan, and purple banding; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Hardness: 6-7 on Mohs scale
Color: Reddish-brown, tan, and purple banding
Luster: Dull/Earthy

Identified March 21, 2026More sedimentary →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Reddish-brown, tan, and purple banding; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Formation & geological history

Formed through the accumulation and cementation of mineral grains (mostly quartz) in ancient riverbeds or coastal environments. The banding represents 'cross-bedding' or rhythmic deposition layers, likely from the Phanerozoic eon. This specific specimen has been water-shaped and smoothed into a 'cobble'.

Uses & applications

Used primarily as decorative stone, aquarium landscaping, or building material (when in brick form). Occasionally used for low-cost lapidary work like rock tumbling.

Geological facts

The distinct purple and red hues are caused by varying concentrations of iron oxide (hematite) and manganese during the lithification process. Water-worn stones like this are often referred to as 'river rocks' or 'beach cobbles'.

Field identification & locations

Identify in the field by the visible sand-sized grains and the characteristic layered 'stripes' that do not wrap completely around like a vein would. Common in sedimentary basins, river mouths, and glacial till. For collectors, look for high color contrast between bands.