Acton Shale is a grey to black thinly laminated silceous shale containing graptolites. It is generally leached, and frequently silicified. The colour of the beds alternates between grey and black, but where weathered, it changes to whitish grey. The graptolites appear on the bedding planes as black films. In Canberra, the Acton Shale appears in several outcrops in Acton, in two bands through Aranda, through Bruce near the Calvary Hospital, on the Bruce Ridge behind Lyneham. Also another band starts under the University of Canberra in Belconnen, and heads north east through Lawson and Giralang and folded and faulted into several bands in Crace on Gungahlin Hill. Another band is found on the west side of Queanbeyan, extending north to Dundee, and south around the east side of Jerrabomberra Hill.