sedimentary

Banded Siltstone

Siltstone with rhythmic bedding

Hardness: 6-7 (Mohs scale); Color: Brown, tan, and dark grey bands; Luster: Dull/Matte; Crystal structure: Microcrystalline clastic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6-7 (Mohs scale)
Color: Brown, tan, and dark grey bands
Luster: Dull/Matte

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Brown, tan, and dark grey bands; Luster: Dull/Matte; Crystal structure: Microcrystalline clastic; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the lithification of silt-sized particles deposited in low-energy environments like river deltas, lakes, or deep marine settings. The bands represent seasonal or environmental changes in sediment deposition speeds and mineral content.

Uses & applications

Used primarily in construction as fill material or decorative stone. High-quality banded specimens are used in lapidary for tumbling and making cabochons or decorative garden stones.

Geological facts

The distinct banding seen here is often referred to as 'rhythmic bedding' or 'varves' if formed in glacial lake environments, documenting historical climate shifts layer by layer.

Field identification & locations

Identify by its fine-grained texture (grittier than claystone but smoother than sandstone) and visible parallel layers. Commonly found in riverbeds and ancient seafloor deposits worldwide.