Inderite, Tincalconite

This specimen, originally labeled as Kernite, is more likely Inderite due to its sharp cleavage and chalky alteration to Tincalconite, a common transformation for this species. It is a display-quality example of the rare hydrated magnesium borate, from Boron, California—a locality known for producing some of the finest specimens of the species. Inderite crystals initially form colourless and gemmy, but exposure to air causes them to turn chalky white. Collectors sometimes coat these specimens to preserve their original appearance. According to Rock Currier on mindat.org, "the white alteration layer can often be removed by soaking the crystals in water for a few minutes". Inderite specimens from Boron are hard to find on the market today, making this desirable and classic material.

Boron, California, located in the Kramer District, is home to the U.S. Borax open-pit mine, one of the largest borate producers in the world. Before the open pit began production around 1958, the site was California’s largest underground mine, though relatively few specimens were recovered from those early workings. Minerals such as Colemanite, Ulexite, Kurnakovite, Inderite, Tunellite, and Hydroboracite were found in crystal-filled pockets in the altered cap rock. During the early years of open-pit mining, collectors were allowed to freely collect on the dumps, resulting in thousands of fine borate specimens entering the market. Today, public access is restricted, with rare exceptions during the town’s annual Boron Gem and Mineral Show. Visitors can still explore the mine’s visitor centre, that also hosts a pile of borate minerals in their parking lot where visitors can collect local minerals.

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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.