How To Tell The Difference
A simple acid sensitivity test can be performed to determine whether a stone is calcareous or siliceous. You will need a few drops of vinegar and an eyedropper. Because this test may permanently etch the stone, select an out of the way area and several inches away from a mortar joint. Apply a few drops of the vinegar to the stone surface about the size of a quarter. If the stone is calcareous, the vinegar will etch the stone. If little or no reaction occurs, the stone can be considered siliceous. Rinse the area thoroughly with clean water and wipe dry.