its white crystal like formation in layer formed on a black rock kinda looks like quatrz and it breaks away easily
Hardness of the sand! Quartz is harder than glass, so will abrade the glass and the abrasion will make it rounded and frosty. Carbonate sand (like coral sands for example) is much softer than glass, so the glass will not abrade. Calcite has a Mohs hardness of 3, Quartz has a Mohs hardness of 7. Window glass has a hardness of about 5.5
