Fluorapophyllite

Fluorapophyllite from Nasik, Maharashtra, India, measuring 77 × 54 × 48 mm and weighing 231 grams. A well-formed piece of the mineral most people simply call Apophyllite, from the same Deccan Traps basalts that produced the Stilbite elsewhere in this sale.

Fluorapophyllite is the fluorine-dominant member of the apophyllite group, a tetragonal mineral that typically forms blocky, pseudocubic crystals with a distinctive pearly to vitreous lustre on its basal face, a result of its perfect cleavage in that direction. Its name comes from the Greek for "it leaves", referring to the way it flakes apart along that cleavage when heated, a property noted by early mineralogists. Like the Stilbite it so often accompanies, it crystallised from late-stage, low-temperature fluids filling the gas cavities of the cooling Deccan basalt flows.

Nasik and the surrounding Maharashtra basalt quarries are the source of most of the world's cabinet-grade Apophyllite, and the combination of Apophyllite and Stilbite from this region is one of the most widely recognised zeolite associations in the hobby. This piece is from the David Vince Collection, and its clean, blocky crystal form makes it a good representative of the species.