Apatite: a hardness reference point that comes in surprising colors

Apatite is the reference mineral for 5 on the Mohs scale, moderately soft, and it occurs naturally in a wide range of colors including blue, green, yellow, and purple, occasionally vivid enough to be mistaken for more well known and more valuable gems. Because of its relative softness, apatite is not commonly used in jewelry meant for daily wear despite attractive color in some specimens, since it scratches and chips more easily than harder stones like quartz or corundum. It is also biologically significant, the mineral making up the hard structure of tooth enamel and bone is a form of apatite, a genuine and often surprising fact for people encountering the mineral for the first time.