apatite - a common complex mineral consisting of calcium fluoride phosphate or calcium chloride phosphate; a source of phosphorusatomic number 15, P, phosphorus - a multivalent nonmetallic element of the nitrogen family that occurs commonly in inorganic phosphate rocks and as organic phosphates in all living cells; is highly reactive and occurs in several allotropic forms atomic number 65, Tb, terbium - a metallic element of the rare earth group; used in lasers; occurs in apatite and monazite and xenotime and ytterbite atomic number 69, thulium, Tm - a soft silvery metallic element of the rare earth group; isotope 170 emits X-rays and is used in small portable X-ray machines; it occurs in monazite and apatite and xenotime mineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition fluorapatite - a form of apatite in which fluorine predominates over chlorine |