Natural Blue Apatite Smooth Roundel Beads StrandSold per 8 inches strand & Sizes from 4mm to 7mm approx.Apatite is one of a few minerals produced and used by biological micro-environmental systems. Apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the major component of tooth enamel and bone mineral.