Niobokupletskite, Calcio-Ancylite-(Ce), Catapleiite, Arfvedsonite, Fluorite, Aegirine, Analcime, Feldspar

This specimen features a matrix composed primarily of analcime and colourless feldspar, with dark arfvedsonite and aegirine prisms running through it in several places. The red arrow is pointing to the area where some red, calcio-ancylite-(Ce) crystals can be found. Notably, there is a substantial amount of niobokupletskite present, tucked into various crevices across the piece. 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 crystals range in colour from yellowish-brown to silvery-brown. Niobokupletskite was originally discovered and collected by Peter Tarassoff on July 12, 1970. 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. Also present is a significant amount of light brown catapleiite, some of which shows a subtle iridescent sheen. Hidden among the catapleiite aggregates are a number of very small purple and green fluorite crystals. Altogether, this is a mineralogically diverse and highly representative specimen from one of the world’s most celebrated mineral localities.

Mont Saint-Hilaire is considered one of the most mineralogically diverse localities in the world, having produced hundreds of rare and unique mineral species—including many of the finest best-of-species specimens ever found. The entry on mindat.org states that there are 440 different species found there, and this quarry is the type locality for 73 of them. Once accessible to collectors, the quarry is now under strict control, with field collecting entirely prohibited. As a result, specimens like this one have become increasingly scarce and sought after by collectors.

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This specimen comes from the collection of Dr. Peter Tarassoff, a prominent figure in mineralogy, particularly known for his work at Mont Saint-Hilaire (MSH). His diligent collecting and examination efforts have led him to be the first to identify at least 35 species and discover 12 new species, not only at MSH but also at other alkaline localities. Dubbed the "Dean" of Mont Saint-Hilaire collectors, Peter was honoured with the naming of the new species petarasite in 1980. He has authored or co-authored numerous mineralogical articles and has been a member of the Mineralogical Association of Canada since 1964. Additionally, Peter has volunteered at the Redpath Museum for the past 21 years, where he was formally appointed the Honorary Curator of Mineralogy. In recognition of his significant contributions to mineralogy, Peter was awarded the 2017 Pinch Medal.