Categories David Erratic, the Arboretum, Walsall Post author By David Post date 10 August 2011 According to the plaque the boulder is rhyolitic lava from north Wales, brought to the midlands on the Ice Age glaciers. It was found in Fullbrook and raised in its current position by the main lake in the Arboretum in 1925. ← Young coot → Tortoiseshell butterfly on a thistle flower