Complex sentence: Dolomite is a double carbonate, having an alternating structural arrangement of CaO and MgO, and it does not rapidly dissolve or effervesce (fizz) in dilute hydrochloric acid as calcite does.
Split into simpler sentences: Dolomite is a double carbonate, having an alternating structural arrangement of calcium and magnesium ions. It does not rapidly dissolve or effervesce (fizz) in dilute hydrochloric acid as calcite does.