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Formula: Sr4Al8(CO3)3(OH)26.10H2O
Hydrated carbonate containing hydroxyl
Crystal System: Triclinic
Specific gravity: 2.677 measured
Hardness: 3½
Streak: White
Colour: White
Solubility: Soluble in 1:1 hydrochloric acid (AM 72.1025)
Environments
Localities
The only known locality to date (September 2020) is the type locality, the Francon quarry, Montréal, Québec, Canada,
where montroyalite occurs as white translucent hemispheres to 1 mm in cavities in an exposed silicocarbonatite sill,
and as individual grains. Associated minerals include albite,
quartz, strontiodresserite,
calcite, dawsonite,
ankerite, fluorite,
baryte, strontianite,
smythite, marcasite,
pyrite, halloysite and
doyleite
(AM 72.1025, HOM, Mindat).
Montroyalite is a late stage mineral, and it is invariably and intimately associated with
strontiodresserite
(Minrec 37.1.39-40)
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