‘Pom-Pom’ Quartz: A New Gem Material Containing Bassanite Inclusions, from Minas Gerais, Brazil

A new gem material from Minas Gerais, Brazil—consisting of colourless rock crystal with conspicuous spherical inclusions composed of extremely fine acicular radiating needles—entered the market in August 2023 as ‘Pom-Pom’ quartz. Electron microprobe analysis of the inclusions showed mainly Ca (up to about 42 wt.% CaO) and S (up to about 57 wt.% SO3), with some Si and Fe. Powder X-ray diffraction analysis identified the non-quartz phases in the inclusions as cristobalite (SiO2; about 60 wt.%) and bassanite (CaSO4 • 0.5H2O; about 35 wt.%), plus minor anhydrite (CaSO4; about 5 wt.%). Infrared spectroscopy confirmed the presence of bassanite, cristobalite and a small amount of anhydrite. This discovery represents the first occurrence of bassanite hosted in quartz.