Pyrophyllite is a sheet-silicate mineral belonging to the clay family and is composed of aluminium silicate hydroxide (AlSi2O5OH). Pyrophyllite occurs in phyllitic and schistose rocks.
Pyrophyllite has low thermal conductivity and a low coefficient of expansion. It is resistive to corrosion from molten metals and slag. It is also inert, nonabrasive, and absorbent, and exhibits low shrinkage when fired. These properties make it suitable for use in refractory bricks and monoliths, foundry facing, ceramics, paint, plastics and as an insecticide carrier.
Pyrophyllite is found mainly in volcanic rocks, where it formed by hydrothermal alteration of feldspars in rhyolite, dacite, and more rarely in andesite.
Although the vast areas of volcanics in eastern Victoria suggest potential for economically viable deposits of pyrophyllite, there are few recorded occurrences, possibly because it is difficult to distinguish pyrophyllite from minerals such as muscovite, sericite and talc, or because it has not been an exploration target. It is also possible that the hydrothermal conditions necessary for formation of large masses of pyrophyllite have not occurred in Victoria. The prospects for discovery of pyrophyllite deposits appear to be better in parts of the Snowy River Volcanics (Devonian) and areas such as Rhyolite Creek (Cambrian volcanics) than they are in the Silurian volcanics.
There has been no comprehensive exploration for pyrophyllite in Victoria. However, there are favourable geological environments in the State and numerous occurrences of pyrophyllite have been encountered in exploration for gold and base metals, which suggests that there is good potential for discoveries.
- Industrial minerals and rocks of Victoria - Geological Survey of Victoria Report 102
- Geological History of Victoria
- Victoria's Minerals, Petroleum and Extractives Industries - Statistical Review
To create your own maps online and in real time, plan exploration activities by viewing land status, or download GIS data to add to your own maps, visit GeoVic.