Marine minerals are a potential source of calcium and magnesium for nutritional supplementation. This study analysed the solubilisation of calcium and magnesium from the skeletal remains of Lithothamnion calcareum. Scanning electron microscopy analysis demonstrated a nonporous microstructure. Spectrophotometric determination showed that the calcium and magnesium contents were 30.01 and 6.22% (w/w), respectively. Solubilisation of calcium and magnesium was highly pH dependent. The temperature-dependent solubilisation of calcium fitted the shrinking core model. The apparent activation energy for calcium solubilisation was 28.6 kJ mol−1. Inclusion of caseinophosphopeptides (CPPs), casein-derived mineral binding peptides, during the solubilisation of calcium and magnesium appeared to decrease the extent of calcium solubilisation at pH 6.0 and 8.0. The results herein have implications for the choice of optimal pH conditions for the sustained release of calcium and magnesium from marine mineral sources.