High Calcium "Hi-Cal" is a general term given to a limestone or lime product that contains a naturally occurring amount of calcium carbonate or calcium oxide greater than 95%. Typically, the next major defining specification is magnesium carbonate or oxide and that is limited to less than 5%. Dolomitic When limestone contains a certain proportion of magnesium, it is called dolomite, or dolomitic limestone. Ideally, this is a one to one molar ratio of calcium to magnesium carbonates. Typical magnesium carbonate concentrations range from 35 to 46%, by weight.