Niobokupletskite, Kupletskite

This thumbnail specimen from the Desourdy Quarry, Mont Saint-Hilaire, features a kupletskite crystal richly covered in delicate tufts of niobokupletskite. These fine, acicular crystals (classified as Type III) radiate outward in a distinctive broom-like habit, a form that earned the humorous nickname “witch’s broom astrophyllite” in Rocks & Minerals (Wight & Chao, 1986). The niobokupletskite ranges in colour from yellowish-brown to silvery-brown. Collected by Peter Tarassoff on July 12, 1970, this specimen comes from the original discovery pocket, which also produced large analcime crystals. Although a secondary occurrence has been reported in India, it has not yielded material of collector interest, leaving Mont Saint-Hilaire as the only effective source of fine specimens of this rare titanium–niobium silicate. With its classic provenance, historic significance, and distinctive aesthetics, this is a highly desirable piece for collectors of Mont Saint-Hilaire minerals and rare species worldwide.