St. Lawrence deposit, Leeds Township, Leeds and Grenville Counties, Ontario, Canadai

Regional Level Types
St. Lawrence deposit	Deposit
Leeds Township	Township
Leeds and Grenville Counties	County
Ontario	Province
Canada	Country

The St. Lawrence Wollastonite deposit occurs within a horseshoe shaped band of quartzite open to the east. The deposit is composed of calc-silicate and silicate skarn layers interbanded and strongly folded within the enveloping quatzite. The southern boundary of the skarn is in thermal metamorphic contact with a gabbroic intrusive which has a syenitic and late pyroxenite phase. The entire package has undergone granulite facies metamorphism. Wollastonite skarn formation is limited to the inner portion of a southwest plunging fold which closes to the west. The Wollastonite skarn zones present within this inner fold cover an area of 275 acres, of which 120 are included in the St. Lawrence deposit property. Wollastonite skarn (ca. 9.6 Mt) with an average wollastonite content of 41.3% is observed in bands averaging 12 meters folded repeatedly throughout the property. The average mineral content consistently associated with the wollastonite is: diopside/hedenbergite 40%, feldspar (predominantly albite with relatively minor microcline) 10%, quartz 5%, calcite trace <2%, sulfides (pyrrhotite and pyrite) <1% and garnet, graphite, phlogopite trace <1%. The wollastonite skarn typically grades into a calc-silicate skarn with a wollastonite content of >20% and <35% wollastonite. The decrease in wollastonite is generally accounted for by an increase in feldspar content. (from the Canadian Wollastonite website, 2002).

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