Mineral Gallery

Gold, Carnon Stream Works, Perranarworthal, Cornwall, England

Gold is a native element and precious metal which has been prized by mankind for thousands of years for its beauty, malleability and resistance to corrosion. This gold nugget is the largest known to have been found in Cornwall and weighs 1 oz t, 18 dwt. 6 grs. It was found in January 1808 in the Carnon Valley tin-stream works and bought by collector Philip Rashleigh in March of the same year. Rashleigh wrote in his Manuscript (112 Au): 'Native Gold found in Carnon Stream work in Cornwall weighs - 1 oz. 18 pw. 6 gr. Troy this piece has had all the extra matter picked out except a mite in one place the marks of many others remain. The smoothness of the piece shews the great time it has been washed by the water where it was exposed and the hollow parts more rough gives a proof of its not being manufactured'. In the ownership of Mr Wills, a silversmith from Truro, the find was reported in the Royal Cornwall Gazette on 6th February 1808 'this is unquestionably the largest and most beautiful specimen ever found in Cornwall, or probably in any other country'. The paper reported in March 1808 that Rashleigh purchased the specimen from Mr Wills. Mineral analysis undertaken in 2018 indicates that the gold content in the nugget is in the high 90s while other gold nuggets from the Carnon Stream Works, which were analysed, are around the 70s. As a result, it has been suggested that this gold nugget may have been refined and worked into a forgery by the silversmith who sold it to Rashleigh. Rashleigh Collection.

© RIC, photographer A.G. Tindle

Chalcocite with Chalcopyrite, Tincroft Mine, Illogan, Cornwall, England

Steel coloured crystals of chalcocite covering chalcopyrite. This botryoidal variety of chalcopyrite is known as blister copper. The specimen was drawn for Specimens of British Minerals, Selected from the Cabinet of Philip Rashleigh (1797, Volume 1, Plate 9, Figure 4) which states 'Is yellow mammillary copper ore, covered with a thin coat of a bluish-green colour, with crystals of steel-coloured copper ore, composed of prisms having six sides, and truncated ends, formed upon the mammillary copper ore. d One of the steel-coloured crystals magnified. From Tincroft'. Chalcocite is a secondary mineral occurring in or near the oxidised zone of copper sulfide deposits. Rashleigh Collection.

© RIC, photographer A.G. Tindle

Cassiterite Partly Replacing Orthoclase, Wheal Coates, St Agnes, Cornwall, England

Twinned crystals of orthoclase feldspar partially replaced by cassiterite. This rare kind of replacement, or partial pseudomorph, is best seen in specimens from Wheal Coates, which are now world famous. The crystals were locally called "stannite" which should not be confused with the tin, copper, iron sulphide of the same name. In Cornwall, cassiterite is concentrated in hydrothermal veins and pegmatites associated with granite intrusions. Cassiterite is the primary ore of tin, the most significant metal mined in Cornwall.

© RIC, photographer A.G. Tindle