Most dolomite is obviously the result of replacement of precursor calcite but certainly not all.
多数白云石显然是原来方解石交代的结果，但肯定不是全部。
2
Carbonate cement is universally more than 10% in sandstones of the upper Yungang formation in Yungang Grottoes area. It's mainly composed of ferriferous calcite and ferriferous dolomite.