This specimen appears to be composed of compacted volcanic ash with inclusions of small volcanic bombs, or lapilli, This type of bomb is referred to as a " cow pie" bomb, and is the result of fluid magma falling from a moderate height and reaching ground level before solidifying. It was collected from Gilwern Hill quarry, Howie, near Llandrindod Wells. This area is part of the Builth inlier. and is characterised by volcanaclastic rocks of the lower to middle Ordovician period, probably resulting from nearby volcanic activity.