Calcareous Ash

Notes:

The ashes are of blue, green or purple colour and varied in texture from coarse breccia or conglomerate to fine trappean grits. The fine grits are often porphyrytic, expecially the purple variety. The blue ash is highly calcareous and is sometimes referred to as an Ashy Limestone of Limestone Ash. This calcareous ash was extensively used in the building of Colbert Station. The green ash horizons are dominant and contain abundant large sized pieces of limestone as well as fragments of grit, slate, trap and ash. Fossils, mainly encrinite stems, are sometimes observed in the ash, and are abundant in the embedded limestone fragments. The ash horizons are found alternating with beds of Visean limestone. They are easily worked, friable and not durable.