Apatite, number 5 on the Mohs scale of hardness, is one of the first minerals that students of geology learn. Because it was commonly confused with other minerals, apatite was not recognized as a distinct mineral species until the late 18th century. The name apatite is derived from the Greek wordά which means "to deceive." Despite what early mineralogists may have thought of its "deceptive" nature, over the next two centuries apatite was gradually recognized to be the most common phosphate mineral in the Earth’s crust and lithospheric mantle where it subsequently acts as a major reservoir for P, F, Cl, OH, CO2, and many trace elements including the rare earths. This issue introduces apatite as a ubiquitous accessory mineral, which is also related to a supergroup family of over 40 other minerals, and then explores its multi-varied roles as a recorder of both terrestrial and extraterrestrial metasomatic and igneous processes, as a thermochronometer over a wide pressure-temperature range, and as a mineral with numerous technological and biological applications.
