sedimentary

Banded Ironstone / Jasper Siltstone

Siltstone with Iron Oxide Hydrates (SiO2 with Fe2O3/FeO(OH))

Hardness: 6-7 on Mohs scale. Color: Earthy brown, terracotta, yellowish-tan, and orange banding. Luster: Dull to earthy, satiny when polished. Structure: Microcrystalline with distinct sedimentary bedding planes. Specific gravity: ~2.6-3.0.

Hardness: 6-7 on Mohs scale
Color: Earthy brown, terracotta, yellowish-tan, and orange banding
Luster: Dull to earthy, satiny when polished

Identified July 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in ancient sedimentary environments through the deposition of fine-grained mud, clay, and iron-rich silica minerals. The distinct color banding represents changes in oxidation state and mineral composition during layering.

Uses & applications

Used primarily as decorative pebbles, lapidary material, tumbled stones for rock tumbling enthusiasts, and landscaping.

Geological facts

Banded siltstones and jaspers are often tumbled smooth by natural stream action, creating rounded 'river rocks' with preserved original sedimentary layers visible as horizontal stripes.

Field identification & locations

Can be identified in the field by its distinctly layered appearance, fine-grained smooth texture, and inability to be scratched easily by a steel knife. Frequently found in riverbeds and gravel deposits.

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