Apophyllite and other zeolite-type minerals from the Whin Sill of the northern Pennines

Apophyllite, analcite, chabazite, prehnite and stilbite are described from pectolite-, chlorite-, calciteand quartz-bearing veins and joint coatings in the late Carboniferous quartz dolerite of the Whin Sill of the northern Pennines. These veins represent the final hydrothermal stages in the sill's emplacement and are not related to the widespread lead-zinc-barium-fluorite mineralization of the northern Pennine orefield. Thermogravimetric studies of apophyllites from the two Whin Sill occurrences reveal that at one locality the minreal is fluorapophyllite, at the other hydroxyapophyllite.