The Wrekin is a prominent hill near the town of Telford. The sedimentary rock types are varied around the area, but lava and volcanic ash (tuff) from various volcanic eruptions form this famous landmark. However, The Wrekin itself is not a volcano, and never was. The primary igneous rock on the Wrekin is rhyolite; this has a pinkish colour and is usually banded as it is a slow cooling viscous extrusive rock. A particularly good outcrop of rhyolite exists as you drive between Wellington and Shrewsbury on the new A5 by-pass. Intrusions of igneous rock have been quarried in the past at nearby Ercall Quarry. Here, the main type of igneous rock that can be found is Granophyre. At Ercall Quarry itself, you can see the contact (boundary) between Precambrian rocks and the younger (Cambrian) sedimentary rocks. In the vicinity these contain fossils from the period associated with the explosion of life.