The quarry at Mont-Saint-Hilaire is one the most prolific localities in the World with currently 430 mineral species identified of which 69 are type locality minerals (ref. mindat.org). Anyone familiar with the Poudrette Quarry will recognize serandite (NaMn2Si3O8(OH)) as the most sought after by mineral collectors. In most and best cases, serandite will form as short to elongate blocky pink to salmon coloured crystals and more rarely as bladed or tiny acicular crystals.
Lately, the new mineral schizolite (NaCaMnSi3O8(OH)) was re-instated as a valid species. This new mineral of the serandite-pectolite series was previoulsy labelled marshallsussmanite from 2013 to 2018. The later name was dropped and replaced by schizolite. Collectors are invited to read the Mineralogical Association of Canada Special Publication #14 (published by the Mineralogical Association of Canada) for a more detailed history. At the Poudrette Quarry, schizolite is found as bladed elongate pale pink crystals with pinacoid terminations and is characterized by one cleavage.
Without chemical analysis, it is difficult to definitely ascertain the identity of some crystals (serandite or schizolite), especially that both species are often found on the same specimen. However, on the basis of colour, crystal habit and crystal grouping, the difference may often be made.
It is interesting to note the Poudrette Quarry is also known for the best crystals of the other end member of the series, pectolite NaCa2Si3O8(OH)). It is fascinating how pectolite differs in colours, general appearance and geological settings with respect to serandite and schizolite.
Collectors who wish to further investigate the mineral species of this series and find excellent photographs are invited to consult the mindat.org website as well as the Mineralogical Association of Canada Special Publication number 14 Mont Saint-Hilaire: History, Geology, Mineralogy book.
Text published: January 2020.