Dolostone differs from limestone because dolomite contains which element in addition to calcium?

• A. Magnesium
• B. Sodium
• C. Potassium
• D. Aluminum

Answer: (A)

Dolostone is defined by the mineral dolomite, which includes magnesium in addition to calcium. The chemical formula CaMg(CO3)2 shows magnesium as the extra element beyond calcium, whereas limestone is mainly calcium carbonate (CaCO3). So the key difference is the presence of magnesium. The other elements listed aren’t part of the dolomite structure, as they belong to different mineral families (sodium, potassium in feldspars; aluminum in clays and related minerals), which is why magnesium is the distinguishing addition.