sedimentary
Banded Siltstone
Siltstone (primarily SiO2 with clay minerals)
Hardness 3-4 (Mohs), color: greyish-green with lighter tan/white bands, dull/earthy luster, fine-grained clastic structure, lacks prominent cleavage.
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Physical properties
Hardness 3-4 (Mohs), color: greyish-green with lighter tan/white bands, dull/earthy luster, fine-grained clastic structure, lacks prominent cleavage.
Formation & geological history
Formed from the lithification of silt-sized particles deposited in low-energy environments like river floodplains, lakes, or deep-sea settings. The banding indicates seasonal or episodic changes in sediment supply.
Uses & applications
Commonly used as fill material or aggregate in construction. High-quality specimens are used for decorative stone markers or educational geological samples.
Geological facts
Siltstone is finer than sandstone but coarser than shale. The distinct rhythmic layering seen here is known as rhythmic bedding, which can often be used by geologists to track ancient climate patterns.
Field identification & locations
Identified by its visible layering and gritty feel on the teeth (unlike smooth shale). Commonly found in sedimentary basins and riverbeds.
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