There was china clay at Dowran, where I lived for a few months. The owners of the campsite said how if you dug, it was bright white clay everywhere.

The gwennap stuff is definately kaolin from rotten feldspars, whereas I thought that "fireclay" was usually obtained from the seat earth of coal seams.

There was a fire clay pit at Pennance on the flank of Carn Marth and is marked on the OS map

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R.M.Barton in his 1966 edition of the History of the Cornish China clay industry has a small reference to something here:
"The Clay shipped from Penryn was raised at St.Day in the Carnmenellis granite, this small pit having been opened in 1870 (min stats UK, Mems geol survey 1870)"

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Further to the original message, the old quarry at Gregwartha, about 1/2 mile down the Four lanes - stithians road, shows up very white on the Google earth view and was shownas an old quarry on the 1908 map. But one report says this is "Freestone"
Some other useful info:
"Near St. Day the decomposing granite is utilised for the
manufacture of bricks, and the factory turns out over a million annually. The granite is decomposed for a depth of about 50 feet, and was formerly used for china clay, but was unable to compete with the superior clays of the St. Austell district. On account of the gritty nature of the clay the individual bricks are cut by hand. Those produced from this decomposing granite have smooth faces, but their edges are imperfect. Some of the decomposed elvans have also been worked commercially for their clay products. Between Carharrack and Lanner clay pits have been formerly opened on an elvan for china clay and bricks. Similar dykes have also been worked as clay pits at Sparry Bottom, in the parish of Gwennap, at Carnon Downs, and at Wheal Baddon."

Ref: THE GEOLOGY OF FALMOUTH AND TRURO
AND OF THE MINING DISTRICT OF CAMBORNE
AND REDRUTH.

J. B. HILL,, E.N, AND D. A. MacALTSTER, A.R.S.M., F.G.S.
WITH PETROLOGICAL NOTES BY J. S. FLETT, M.B., D.Sc.
1906

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The freestone quarry is the Duck stone I referred to

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Yes, Sparry Bottom was the one in Carharrack that I referred to early in this thread. I believe it was filled with rubbish come the end. Nothing new there!

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The freestone quarry is the Duck stone I referred to

I didn't realise until I checked that all these Duckstone and freestone type terms are stonemason descriptions and actually cover a range of rock types. Strange to see it in geological reports from last century!

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