Perlite was quarried on the north shore of Francois Lake, 22 kilometres south of the town of Burns Lake.

The deposit is underlain mainly by Upper Cretaceous to Lower Tertiary rocks correlated with the Ootsa Lake Group. These comprise shallow to medium dipping, devitrified (in part), banded rhyolites, rhyolite breccias, spherulitic rhyolites and tuffs. This series of rocks has a general strike of 040 degrees and an average dip of 30 degrees to the northwest.

The quarry on the lake shore exposes a 2-metre thick bed of dark grey to black, medium grey weathering perlite over a distance of 15 metres in sharp contact above and below with cherty rhyolite. The bed strikes northeast and dips 15 to 35 degrees northwest. The rock exhibits typical onion-skin texture with radiating fractures perpendicular to strike. In places it is brecciated and siliceous with pronounced flow banding.

North of the lake, 300 metres, a similar perlite bed, 15 metres thick, striking northeast and dipping 30 degrees northwest, is exposed intermittently for 110 metres along an access road. At the north end of the roadcut, fresh perlite is exposed continuously for 50 metres. The bed is underlain by coarse grey tuff.

Perlite from both sites expanded a similar amount to that tested at the Frenier deposit (093O 072), when heated by a hand- held propane torch (Fieldwork 1989, p. 483). A sample of perlite tested by CANMET exhibited the following characteristics (Fieldwork 1990, pages 265 to 267):

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Per cent water loss when heated to 800 degrees Celsius: 3.0

Softing temperature (degrees Celsius): 1250-1270

During the period 1949 to 1953 Western Gypsum Products Ltd. of

Winnipeg mined approximately 1587 tonnes of perlite.