A Scottish ‘diamond’ specimen rediscovered and re-identified: the first Scottish occurrence of piemontite

Abstract

Synopsis A possible occurrence of diamond near Ben Hope in Sutherland was described in 1901. For most of the 20th century, the specimen had been assumed lost, and thus the identification could not be verified. This specimen has recently come to light. Re-examination shows that the specimen contains no diamonds, but rather contains a very unusual assemblage of piemontite–spessartine–hematite–braunite–muscovite–K-feldspar–quartz. This is the first Scottish occurrence of true piemontite. Revisiting the original locality, no in-situ exposures were found, but this lithology forms a distinctive component of glacially transported boulders over an area to the east and south of Ben Hope. It is almost certainly derived from the local Moine, and represents a unit with an oxidized, coarse clastic protolith. If found in situ, this unit may be a useful marker bed in the otherwise homogenous psammitic rocks of the Moine in this area.