Lithothamnion calcareum, or Red Sea Algae, is harvested in the pure waters of the north Atlantic ocean. Lithothamnion absorbs calcium and magnesium into its cell walls to create a rigid honeycomb cell structure. It’s this unique structure and the 72 trace minerals absorbed from the sea that make the calcium in Aquamin more bioactive than calcium derived from limestone and why I included it in my first-ever, full-spectrum bone health supplement.