sedimentary

Beach sand with a dark pebble

Unconsolidated siliciclastic sediment, chiefly quartz and feldspar; dark pebble likely basalt or volcanic rock

AI-generated identification · may be incorrect

Grains are mostly sand-sized (0.0625–2 mm), angular to subrounded, with white, gray, tan, and black colors; quartz has Mohs hardness 7 and vitreous luster. The larger dark clast appears fine-grained and weathered, but cannot be identified confidently from the image alone.

Identified August 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Produced by weathering, erosion, transport, and wave sorting of surrounding bedrock; the sediment is geologically young and continually reworked in a beach environment. The dark pebble may derive from older basaltic or other mafic volcanic rocks.

Uses & applications

Used locally in landscaping, filtration, sandblasting, glass manufacture, and construction aggregate; ordinary beach sand and the pebble have negligible collector value.

Geological facts

Beach sand composition reflects its source rocks and transport history; magnetite-rich dark grains may be attracted to a magnet. Grain-size sorting and rounded grains indicate abrasion and wave action.

Field identification & locations

Identify with a hand lens, magnet, streak test, and acid test: quartz is hard and nonmagnetic, while magnetite is magnetic; basalt is dark, dense, and fine-grained. Common worldwide along coasts and lakes.