Sandstone (Flagstone)

Physical Properties

Hardness: 6-7 (Mohs scale); Color: Tan, grey, yellowish-green (due to algae/lichen); Luster: Dull/Earthy; Crystal structure: Clastic (granular texture); Cleavage: None, breaks into slabs along bedding planes.

Formation & Geological History

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, typically in riverbeds, deserts, or coastal environments. This specimen likely dates from the Paleozoic or Mesozoic eras depending on regional geology.

Uses & Applications

Commonly used in construction for paving, walkways, patios (flagstone), wall cladding, and landscaping because of its durability and ability to be split into flat slabs.

Geological Facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The layers seen in sandstone can preserve ripples from ancient water currents or wind, providing a 'fossilized' record of ancient environments.

Field Identification & Locations

Identify in the field by its 'gritty' feel (like sandpaper) and visible layers or bedding. It is found globally in sedimentary basins. Collectors often look for examples with distinct cross-bedding or fossil inclusions.

Identified on: 4/19/2026

Mode: Standard