Discovered as an important source for minerals by collectors in 1995, Dolyhir Quarry, near Old Radnor, Powys, has rapidly become known as one of the most diverse mineral locations in the British Isles. Extensive research by museum curators and amateur mineral collectors has produced more than 70 different mineral species, many of which were new to the British Isles. Several different 'assemblages' or groups of minerals have been recorded, each of which is related to different geological events that have occurred in the area.
The quarry is situated directly on the Church Stretton Fault, where Precambrian basement rocks are overlain unconformably by Silurian limestone. Various igneous intrusions occur locally, alteration of which has released many rare elements that have subsequently recrystallized within fractures in the Silurian and Precambrian rocks. Later, supergene (near surface) weathering of mineral veins within the limestone has produced a suite of rare secondary minerals.
Active quarrying continues to provide changing cross-sections through the geological units and frequently reveals exiting new mineral discoveries that are documented by researchers. The most recent discovery is the identification of 'Alpine-type' fissures, more common in Snowdonia, or as the name suggests - the Alps.