Aragonite - 50#
(33% CaCO3) When the price of aragonite spiked a few years ago, we tried to steer growers toward the chemically identical Calcitic Limestone, but they were having none of it. The internet forums said to use calcium carbonate from oyster shells, not from pulverized rock, so oyster shells they must have! We are acquiescing and listing aragonite again. Aragonite is even lower than calcitic lime in magnesium, so it's the ideal choice for soils with excessive magnesium. Mined from the deposits that create the white sand beaches of the Bahamas. More expensive than calcitic lime, but less expensive than a tropical vacation. Feed quality.