- Pure Powder,- High Percentage of Calcium.NOW Calcium Carbonate is a Calcium supplement containing one of the highest concentrations of elemental Calcium available. Its high Calcium content makes it an excellent form for the support of healthy bones and teeth.NOW has been selling powdered supplements since 1968 because of their distinct advantages. The powdered form is pure, and free of fillers and preservatives, much lower in cost, easy to digest and can be taken in desired potencies. Powdered vitamins and minerals are truly the best way to take supplements.