Habitat type: Quarry and wet woodland
Size of reserve: 0.6 hectares / 1.5 acres
OS map number: 106
Grid reference: SW 995 587
Best time to visit: All year
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Directions
Take the B3274 off the A30 towards Roche. Drive through Roche and turn left in Trezaise before the church. The tarmac road will finish and the reserve is straight up the track on your right.
Access
Uneven tracks and a small section of boardwalk lead to the rock face.
Geology
This is a geological nature reserve. Molten magma rose from deep below the surface of the earth to form a special granite, with very large crystals, called a pegmatite. The large white feldspars were the first to crystallise from the magma. The spaces between filled with grey quartz, shiny flakes of mica, long black glistening crystals of tourmaline and dull black cordierite.
Pegmatites are important as they are natural concentrators of rare elements such as niobium, cerium and beryllium.
Leftover magma formed a finer-grained granite and then a speckly grey rock, locally called 'blue elvan', which was quarried for roadstone.
Other information
The 'bal' maidens hammered the cut blocks to isolate the feldspar, which was taken up-country and to the continent, via the port of Fowey, to be used for glass making or in pottery glaze.
The site was known as Roche Glass Mine or Polpuff, and articles were written about it in the Mining Journal. The quarry opened in the late 1870s and in August 1879, people were invited to buy shares in a 'bona fide and safe investment'. This was six months before it was put up for auction! We don’t know why quarrying ended, but the Mining Journal records that production was hampered by severe winters on this exposed common. The quarry reopened in 1917, during the First World War, to provide feldspar for electrical porcelain.
The reserve was a gift from Goonvean Ltd.
