Niobokupletskite, Aegirine, Microcline, Calcite

This specimen a section of microcline feldspar with a couple intergrown black aegirine prisms through it. What makes it interesting is in all the nooks and crannies are 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 crystals range in colour from yellowish-brown to silvery-brown. Niobokupletskite was originally discovered and collected by Peter Tarassoff on July 12, 1970—a pocket that also produced large analcime crystals, up to 6 inches in size, now in his personal collection. 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.

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.