A Working quarry, at Loanhead (NS363557) within the Clyde Plateau Carboniferous lavas, is traversed by a tholeiitic Tertiary dyke some 25-30 m wide. Throughout the quarry the lavas are extensively altered and the most prominent secondary minerals are calcite and prehnite. Adjacent to the dyke is an indefinite alteration zone within which garnet has developed in close association with analcime and thomsonite. Contact metamorphism is not apparent. Secondary minerals in the quarried lavas and from the alteration zone have been described by Meikle (1989). The most salient feature of secondary mineral formation central to this paper is that grossular and andradite occur, in situ, in close proximity to the dyke, and only in the amygdales.
