Conneisseur’s Choice: Schizolite: Poudrette Quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM Montérégie, Québec, Canada

Schizolite has undergone some mineralogical ignominy since its description and naming by Winther (1901). Discovered in Greenland (Peterson and Johnson 2005), schizolite was relegated to varietal status in 1955 only to be reinstated in 2018. In addition, two world-famous mineral localities—Mont Saint-Hilaire, Canada, and the Kalahari manganese field, South Africa—have produced the finest examples of schizolite, but these, too, have followed a diverse path until investigations revealed their true identity (fig. 1). This saga is partially explained by schizolite’s chemistry. It forms part of the serandite-schizolite-pectolite series of the wollastonite group (https://www.mindat.org/min-44010. html; accessed March 2023). Serandite, NaMnSi3O8(OH), contains sodium and manganese while pectolite, NaCa2 Si3O8(OH), contains calcium and is manganese deficient. Schizolite, NaCaMnSi3O8(OH), has an ordered crystal structure with Ca occupying the M1 and Mn occupying the M2 octahedral sites (Tarassoff and Horváth 2019). Because of their similar atomic radii, manganese and calcium can substitute for one another, forming manganoanpectolite and/or calcium-bearing serandite. Schizolite, NaCaMnSi3O8(OH), crystallizes in the triclinic system (although originally described as monoclinic) with perfect cleavage on {100} and {001} (https://www. handbookofmineralogy.org/pdfs/schizolite; accessed March 2023). It was this specific property that led to its name, derived from Greek for skhizo, “to split.” Winther (1901) emphasized that after crushing, the sample kept splitting along the cleavage planes such that it was extremely difficult to obtain transverse crystal fragments. Schizolite has a hardness of 5, a vitreous to subvitreous luster, and a specific gravity of 3.09. Crystals are translucent to opaque, pale bright-pink to brown and produce a white streak. Flink (1898) collected the first samples from Greenland in 1897 (Gordon 1924) and described the crystals as pink columns. The type locality is Tugtup Agtakôrfia, Tunulliarfik Fjord, Ilímaussaq Complex, Kujalleq, Greenland (fig. 2), with the type-material housed at the Natural History Museum of Denmark. Fifty-four years after its description, Schaller (1955), in a study of the pectolite-schizolite-serandite series, concluded that schizolite was merely manganoanpectolite and that it be discarded as an unnecessary species name. He based this on chemical analyses of several samples of pectolite, “maganpectolite,” serandite, and schizolite, the last from Greenland. Even so, Ohashi and Finger (1978) later resolved the crystal structure of schizolite but did not suggest reinstatement of the species. It was, therefore, during this period when schizolite was no longer considered a valid species that two significant discoveries were made, one in the Kalahari manganese field in South Africa, and the other in Mont Saint-Hilaire in Canada. Schizolite