Ercall Granophyre (England, UK)

Ercall Granophyre Specimen - The Ercall & The Wrekin, Wellington, Telford & Wrekin/Shropshire, England, UK

This robust specimen is a spectacular example of Granophyre, an intrusive igneous rock sourced from the historically and geologically significant Ercall hill in Telford, England. The Ercall Granophyre forms the basement rock in this area, beneath the famous Ercall Conglomerate, and is a key component of the region's geological history.

The rock is dominated by a striking reddish-brown to pink colour, which is characteristic of the potassium-rich K-feldspar (orthoclase) and quartz that constitute most of the rock's volume. Its texture is the defining feature: it is micro-crystalline with a unique granophyric texture. This texture is named after the rock and is formed when quartz and feldspar crystals grow simultaneously in a finely intergrown pattern, often resembling graphic writing under magnification. This indicates a rapid but not instantaneous cooling of the magma.

The Ercall Granophyre is a notable intrusion, dated to the late Precambrian (Neoproterozoic) era, making it one of the oldest rocks in the region. It is the hard, resistant rock that gives the Ercall hill its form and is the source material for many of the clasts found in the overlying Ercall Conglomerate. Its geological setting—part of the Wrekin-Lilleshall structure and connected to the Uriconian Volcanic Group—makes it invaluable for understanding the ancient magmatic and tectonic history of the UK. This specimen is an excellent display piece for collectors, a superb teaching aid for university students, and a must-have for anyone interested in UK igneous geology.

Origin: The Ercall, Wellington, Telford & Wrekin/Shropshire, England, UK
Rock type: Granophyre
Size: ~10(L) x 7(H) x 5(W) cm (see scale cube), 302 g