sedimentary
Sandstone with Vitrinite/Coal inclusions
Arenite with Carbonaceous inclusions
Hardness: 6-7 (sandstone matrix), 2-3 (carbon inclusions); Color: Tan/Grey matrix with black/dark grey inclusions; Luster: Dull (matrix) to Vitreous/Sub-metallic (inclusions); Crystal structure: Clastic (matrix), Amorphous (carbon); Cleavage: None/Conchoidal in coal pieces
- Hardness
- 6-7 (sandstone matrix), 2-3 (carbon inclusions)
- Color
- Tan/Grey matrix with black/dark grey inclusions
- Luster
- Dull (matrix) to Vitreous/Sub-metallic (inclusions)
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Physical properties
Hardness: 6-7 (sandstone matrix), 2-3 (carbon inclusions); Color: Tan/Grey matrix with black/dark grey inclusions; Luster: Dull (matrix) to Vitreous/Sub-metallic (inclusions); Crystal structure: Clastic (matrix), Amorphous (carbon); Cleavage: None/Conchoidal in coal pieces
Formation & geological history
Formed through the accumulation of sand-sized mineral grains and organic plant matter in high-energy environments like rivers or deltas. Over millions of years, lithification preserves the sand as rock and carbonizes the plant material into vitrinite or coal.
Uses & applications
Sandstone is widely used in construction, architectural facades, and as an abrasive. The carbonaceous inclusions are of interest to geologists for paleo-environmental reconstruction.
Geological facts
The black inclusions are remnants of ancient plant material that have undergone carbonization. Sandstones with clear organic patterns can sometimes transition into petrified wood or contain significant fossilized imprints.
Field identification & locations
Identify in the field by the granular, sandpaper-like feel of the matrix and the presence of brittle, black, coal-like flecks or streaks. Commonly found in sedimentary basins and riverbeds near ancient forest deposits.
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