This showing of expandable volcanic glass lies in an area underlain by basaltic flows and breccias and by rhyolite flows of the Tertiary Masset Formation. The entire sequence dips gently to the northwest.

A roadcut northwest of Florence Creek, 15 kilometres southwest of Port Clements, exposes black, medium-grained, feldspar porphyritic glassy dacite for a length of 300 metres. The dacite pops violently when heated with a propane torch, instead of expanding gradually as for a nearby perlite occurrence (103F 022). A sample tested by CANMET exhibited the following characteristics (Geological Fieldwork 1990, pages 265 to 267): Per cent weight loss when heated to 800 degrees Celsius: 1.2 Softening temperature (degrees Celsius): 1210-1240 Density before heating (kg per cubic metres): 2570 Density after heating to softening temp. (kg per cubic metre): 928