The area of the Koksilah quarry is underlain by sandstone, shale and conglomerate, probably of the Extension or Protection formations, Nanaimo Group. Sandstone beds up to 6 metres thick overlie a 6- metre thick sequence of soft sandstone, shales and conglomerates which in turn overlie a sequence of shale. The formation strikes 010 degrees and dips 25 degrees to the north.

Joints cut the formation in a general north and south direction. They are steeply inclined, dipping both ways from the vertical. In places these joints are 3 to 4 metres apart, but usually they are much closer. Cross joints, at right angles to the above joints, are very irregularly developed, with a prevailing dip of 70 degrees to the south. On the whole the rock is reported to be considerably shattered.

The heavy sandstone beds show a fairly uniform blue-grey colour which is interrupted by coarser streaks and fossil-bearing bands. The rock is fine grained and of even texture.

The Koksilah stone may be seen in Craigdarroch Castle and in the Methodist church at the Corner of Pandora and Quadra streets in Victoria. No production figures are available.