mineral/sedimentary

Manganese Dendrite on Siltstone

Manganese Oxide (pyrolusite or psilomelane) Dendrites

Hardness: 3.0-4.0 for matrix, 6.0 for dendrites; Color: Black/Dark brown branching patterns on tan/cream matrix; Luster: Dull to sub-metallic; Crystal Structure: Monoclinic/Orthorhombic; Specific Gravity: 4.5-5.0 (mineral portion)

Hardness: 3
Color: Black/Dark brown branching patterns on tan/cream matrix
Luster: Dull to sub-metallic

Identified July 5, 2026More mineral/sedimentary →

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Physical properties

Formation & geological history

Formed by the precipitation of manganese-rich mineral solutions filling cracks between layers of sedimentary rock (limestone, siltstone, or shale). These branching patterns are pseudofossils, formed via crystal growth in fractal patterns.

Uses & applications

Primarily collected as geological specimens, used in decorative lapidary work, educational tools for demonstrating crystal growth and pseudofossils.

Geological facts

These patterns are often mistaken for fossilized ferns or mosses due to their tree-like (dendritic) structure, but they are purely mineralogical and not organic in origin.

Field identification & locations

Identify by the fractal-like black branching patterns that usually sit on the surface of bedding planes. Commonly found in Solnhofen limestone and various sandstone/siltstone formations globally.

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