Inorganic Limestone and Inorganic Gypsum I read that limestone is made from the compaction of marine animals' bones. But, I am unable to find out why limestone could not have been produced from calcium occurring naturally (5th most abundant element in earth's crust) in the Earth Crust and in the mantle?

Is gypsum also produced from marine animal's bones?
Limestone is a sedimentary rock made up mainly of the mineral calcite (calcium carbonate). It may be made up of biogenic calcite such as shells or inorganic calcite deposited as fine grained "micrite" although some micrite may also have a biological origin.

Animals don't have bones made from gypsum so all gypsum deposits have non-biological origin.