Trevalganite is a rock specific to this area , which is close to the Granite Contact (Lands End Granite) .
Granite with Feldspar has been transformed during the high temperature phases of mineralisation to mainly
Tourmaline with the Feldspar unchanged or replaced by Quartz.
The Modern Standing Stones on the Trevalgan Farm Trail (Private Land) , may be of Trevalganite as might
the recumbent stone behind where the Feldspar Crystals have weathered out - leaving holes in the rock .
A modern Stone Circle to the west may have these Black rocks as well.
Trevalganite in the field walls , as in the Pics from 1977 on the British Geological Survey Website ,
appear to have been covered by Bracken / Scrub.
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Trevalgan Cliff is to the west of St Ives in Gallery 16
Ref: 4517
Date: 05/02/2017
Location: SW 4893 4078