Every serious field geologist carries a small bottle of 10 percent hydrochloric acid to perform this quick field test, used to distinguish the most common carbonate rocks, dolomite and limestone (or marble, which may be composed of either mineral). A few drops of the acid are put on the rock, and limestone responds by fizzing vigorously. Dolomite fizzes only very slowly.
Usage To identify limestone then a drop of hydrochloric acid will ‘fizz’ as CO2 is produced. No fizzing means that the rock is not limestone and resorting to a magnifier could sort out the rock type. Some sandstones fizz because the cement bonding the grains is calcitic, Again this will help to identify a rock. Magnesian limestone needs warm HCl to fizz because the rock contains magnesium as well calcium in its structure.
Example geologists use dissolved hydrochloric acid to identify carbonate rocks.
for example: Limestone is a calcium carbonate rock. The carbonate reacts with the H ion and creates a chemical reaction. When the reaction occurs the mix fizzes (makes bubbles).