Final answer:
Gypsum is not a carbonate rock; it is a sulfate mineral, whereas limestone, travertine, dolostone, and rocks from coral reefs are all carbonate rocks primarily composed of calcite.
Step-by-step explanation:
The type of rock that is NOT a carbonate rock from the list provided is gypsum. Carbonate rocks are primarily composed of the mineral calcite (CaCO3) and include rocks such as limestone, travertine, dolostone, and those formed from coral reefs. Gypsum, however, is composed of calcium sulfate dihydrate (CaSO4ยท2H2O), making it a sulfate mineral, not a carbonate one. Limestone forms through the accumulation of biological debris such as the remains of marine organisms like clams and corals. Travertine is a form of limestone deposited by mineral springs. Dolostone, also known as dolomite, is a sedimentary rock composed primarily of the mineral dolomite (CaMg(CO3)2). Rocks formed from coral reefs are composed of calcium carbonate from the skeletons of coral organisms. By contrast, gypsum is known for its softness and can be easily scratched, differing from carbonate rocks which react with dilute acid due to their calcite content.