In both Recent and ancient limestones, marine cements which have a botryoidal morphology are generally thought to have precipitated as aragonite. However, Upper Cretaceous botryoidal cements from widespread Mediterranean localities, described here, are interpreted as former high-magnesium calcite. Petrographic features indicating an originally high-magnesium calcite mineralogy include rhombic terminations to precursor crystallites and microdolomite inclusions. Minor element concentrations in the botryoids are depleted in strontium relative to calcitized skeletal aragonite. A former calcitic mineralogy for Cretaceous botryoids is in accordance with proposals that ocean chemistry at this time inhibited inorganic aragonite precipitation.