Francon Quarry

Thanks to Peter G.Seroka again for the Woolley book and for his own data.

Francon Quarry (aka St.Michel sill) is a silico-carbonatite sill in Trenton limestone. It is 2m thick, and extends over an area of roughly 1.1x0.5 km. Chilled contact zones reach a thickness of 4-5 cm. The rock, mainly in the central and upper zones, contains many cm-sized vesicles, elongated close to the contatcs. The chilled selvages are intergrowths of dawsonite/feldspar with pseudos of dawsonite after analcime. The central part also contains dawsonite pseudomorphs, feldspar laths, dawsonites, other carbonates (partly calcite and dolomite). There seems to be a second sill of 1.3 m below the main one.

Mineral list: (still very incomplete, bold =type loc.)

Aegirine-augite
Albite
Analcime
Anatase
Ankerite
Baddeleyite
Barite
Calcite
Celestite
Cryolite
Darchiardite
Dawsonite
Dolomite
Doyleite
Dresserite
Fluorite
Franconite
Galena
Gibbsite
Hematite
Hochelagaite
Hydrodresserite
Kaolinite
Marcasite
Montroyalite
Mordenite
Plagioclase
Pyrite
Quartz
Sabinaite
Siderite
Smythite
Sphalerite
Strontianite
Strontiodresserite
Voggite
Weloganite
Zircon



&Suggested reading:

Woolley, A.R.: Alkaline Rocks and Carbonatites of the World. Part 1: North and South America. British Museum (Natural History), London, 1987


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