Calcite (var. Sand Calcite)

Sand calcites are a fascinating mineral oddity formed as calcite crystallizes in sandy soil, capturing sand particles during crystal growth. These crystals typically consist of approximately 40% calcite and 60% sand inclusions. They naturally occur as double-terminated, hexagonal scalenohedrons. The crystals are found within beds of coarse sandstone. This is a notable, well formed and fairly large, example of this phenomenon from South Dakota, USA. Other calcite sand concretions are known from only a few localities worldwide, including the Imperial Valley-Salton Sea area of California. This unique formation process and the resulting distinctive crystal morphology make sand calcites an intriguing subject of study in mineralogy.

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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.