sedimentary

Tumbled limestone or dolostone pebble

Calcite-rich limestone (CaCO₃), possibly dolostone (CaMg(CO₃)₂)

AI-generated identification · may be incorrect

Cream to tan, fine-grained, dull to softly waxy surface, with no visible crystals or cleavage; hardness about 3 for limestone and 3.5–4 for dolostone, and specific gravity roughly 2.7–2.9. The rounded, smooth shape indicates natural water wear or tumbling.

Identified September 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from compacted marine carbonate sediment or accumulated shell material, generally during Phanerozoic marine deposition; the exact age and subtype cannot be determined from the image. Dolostone forms when magnesium-rich fluids alter limestone after deposition.

Uses & applications

Used extensively for aggregate, cement, lime, building stone, and landscaping; attractive pieces are sold as décor or low-cost polished specimens. It is generally inexpensive.

Geological facts

A drop of dilute hydrochloric acid or vinegar typically fizzes strongly on calcite limestone; dolostone reacts weakly unless powdered. The specimen’s unusual elongated shape may reflect abrasion around a harder inclusion or a naturally worn fragment.

Field identification & locations

Common worldwide in former shallow-marine regions and river gravels; likely local or commercially tumbled. Confirm with acid testing, streak (white), and magnification for fossil fragments or rhombohedral dolomite crystals.