Summary of site:
This small abandoned quarry exploited the Tardree Rhyolite and is mineralogically important because tridymite occurs in crystal-lined cavities of the rhyolite lava. Tridymite is a high temperature form of silicon dioxide (silica) better known in its usual form as quartz. It is the stable form in the temperature range 870 to 1,470 degrees centigrade but has survived as miniature crystals in this area and particularly in this quarry.
The general geology of the Interbasaltic Formation of which the Tardree Rhyolite Complex is a part is described in the account of Sandy Braes (site 517).