Niobokupletskite, Analcime, Aegirine, Calcio-Ancylite-(Ce)

This specimen consists of an analcime crystal intersected by several black prisms of aegirine and some delicate tufts of niobokupletskite tucked in a few of the nooks and crannies of the crystal. These fine, acicular 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. To add even more complexity specimen’s mineralogical significance is the presence of calcio-ancylite-(Ce) crystals, a cerium-dominant rare earth carbonate that occurs as tiny grains. Together, this combination highlights the paragenetic complexity and rare element geochemistry for which Mont Saint-Hilaire is celebrated. There are also some The overall composition and contrast make this a highly desirable specimen for collectors of rare species or Mont Saint-Hilaire minerals.