Abridged version of an article originally published in the Monthly Mineral Chronicles volume 5, number 10.
Kaolin, or ‘China Clay’ as it is commonly called, is a hydrated aluminium silicate crystalline mineral formed by the hydrothermal decomposition of granite rocks.
All of the major granite intrusions in Cornwall have been worked for China Clay in the past, but production is centred on the St Austell Granite, which accounts for over 80% of UK output, and which is where Wheal Remfry and other deposits are situated.
The Wheal Remfry China Clay pit lies at the western end of the St Austell granite, and it is thought that granite lies not far below the base of the pit.
Mindat lists nineteen minerals, many of which are typical granite minerals. The minerals listed are: anatase, “apatite”, autunite (questioned), bismutite, cassiterite, dravite, fluorite, kaolinite, muscovite, opal, quartz, rutile, schorl, topaz, torbernite, “tourmaline”, turquoise, wavellite and waylandite. Note that no feldspars are mentioned.
