Beach-rounded limestone cobble with marine bio-borings (pholad/piddock clam holes) — sedimentary Identification & Properties | Geo-Gem
Beach-rounded limestone cobble with marine bio-borings (pholad/piddock clam holes) is a sedimentary. 1) Acid test: Place a drop of cold 10% HCl or white vinegar on a freshly scratched spot. Limestone will fizz readily; dolostone will be weak to nonreactive unless powdered. 2) Hardness: Try a steel nail (Mohs ~5.5) and a copper coin (Mohs…