The igneous rocks of the Stanner-Hanter district near the Welsh border are regarded as part of a larger unexposed development of intrusive types and of pre-Cambrian age. The igneous sequence began with the intrusion of the fine dolerites probably in the form of successive thin sheets or sills. Then followed the intrusion of the gabbros, possibly in the form of a laccolith. This was followed by the injection of the aplogranite magma and the production of its associated hybrids. Late-stage activity on the part of this magma may have caused the widespread epidotization and amphibolization which is so characteristic of the earlier basic types. The other acid types (quartz porphyries) and the later dolerites were next intruded; the relative ages of these are unknown.