Colour variegated reddish or greyish brown; fracture dull and scaly; soft, owing to seatite which occurs both in grains and in larger disseminated concretions.
It also contains radiated zeolite in considerable abundance, in concretions of all sizes: and cubic zeolite has been found at Benyavenagh, but is very rare.
Chalcedony is likewise found imbedded in this rock, but is not very common.
Has been found in seams varying from two inches to four or five feet in thickness, alternating with trap rocks near Ballintoy; associated with the bed of wacke, underlying the upper columnar stratum in the cliffs of Portnoffer on the east of the Giant's Causeway, at Killymorris near the center of the basaltic area, and at Portmore and other places along the eastern shore of Lough Neagh. At Portmore the beds are said to exceed considerably in thickness the dimensions above given. The texture of the wood is often remarkably distinct, and indicates that it is a species of fir. It has even been asserted that the roots and branches of the trees could be traced.
The wood coal at Portnoffer has the exterior surface of some of its fragments penetrated to a certain depth by small nests of augite imperfectly crystallized.