sedimentary
Dendritic Siltstone
Siltstone with Manganese Oxide dendrites (MnO2)
Hardness: 3–4 (Mohs); Color: Light grey to beige with dark brown/black tree-like patterns; Luster: Dull/Earthy; Structure: Clastic; Cleavage: None (fractures into plates); Specific Gravity: 2.6
- Hardness
- 3–4 (Mohs)
- Color
- Light grey to beige with dark brown/black tree-like patterns
- Luster
- Dull/Earthy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3–4 (Mohs); Color: Light grey to beige with dark brown/black tree-like patterns; Luster: Dull/Earthy; Structure: Clastic; Cleavage: None (fractures into plates); Specific Gravity: 2.6
Formation & geological history
Formed from the lithification of silt-sized particles in low-energy aquatic environments. The dark patterns are manganese-rich mineral solutions that crystallized in fractures over millions of years.
Uses & applications
Primarily used as a decorative stone, in lapidary work for cabochons, and as an educational tool to demonstrate pseudo-fossils.
Geological facts
The tree-like patterns are often mistaken for fossilized ferns or plants, but they are purely inorganic crystal growths called dendrites.
Field identification & locations
Identifiable by the flat, plate-like breakage of the siltstone matrix and the branching fractal patterns. Common in Utah and Germany. Collectors should look for high contrast patterns.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary