Through high heat and evaporation the body is reduced to its basic mineral form. (radiant-heart.net)
The material that makes up pteropod shells is aragonite, a common mineral form of calcium carbonate, which is also secreted by other marine organisms to form external skeletal material. (dotearth.blogs.nytimes.com)
Further, the CO2 mixes with the volcanically warmed water below the surface and undergoes chemical reactions within the basalt (the black rock created from rapidly cooling lava) to form carbonate compounds — otherwise known as chalk — effectively locking up the greenhouse gas in mineral form. (scientificamerican.com)