Niobokupletskite, Kupletskite, Analcime

This specimen consists of a section of an analcime crystal intersected with dark brown kupletskite which can be seen dynamically transitioning into more delicate light brown niobokupletskite. These fine, acicular niobokupletskite crystals—classified as Type III—radiate outward in a distinctive broom-like habit, a form that earned the nickname “witch’s broom astrophyllite” in Rocks & Minerals (Wight & Chao, 1986). The crystals range in colour from yellowish-brown to silvery-brown. Niobokupletskite was originally discovered and collected by Peter Tarassoff in 1970, a pocket that also produced large analcime crystals, such as this one. While there is a secondary occurrence reported in India, it has not produced specimens of collector interest, making Mont Saint-Hilaire effectively the only source for quality material of this rare titanium-niobium silicate. Together, this combo-specimen  highlights the paragenetic complexity and rare element geochemistry for which Mont Saint-Hilaire is celebrated. Making this a highly desirable specimen for collectors of rare species or Mont Saint-Hilaire minerals. This specimen was collected by Tarassoff in 1970.