On the Mineralogy of certain Organic Remains from the Laurentian Rocks of Canada

Abstract

T he remains of Eozoön Canadense , a Foraminiferal organism recently discovered in the Laurentian limestones of Canada, present an interesting subject of study, both to the mineralogist and the geologist. For a zoological description of this organic form the reader is referred to the preceding description by Dr. Dawson. The details of structure have been preserved by the introduction of certain mineral silicates, which have not only filled up the chambers, cells, ard canals left vacant by the disappearance of the animal matter, but have in very many cases been injected into the tubuli, filling even their smallest ramifications. These silicates have thus taken the place of the original sarcode, while the calcareous septa remain. It will then be understood that when the replacement of the Eozoön by silicates is spoken of, this is to be understood of the soft parts only, since the calcareous skeleton is preserved, in most cases, without any alteration. The vacant spaces left by the decay of the sarcode may be supposed to have been filled by a process of infiltration, in which the silicates were deposited from solution in water, like the silica which fills up the pores of wood in the process of silicification. The replacing silicates, so far as yet observed, are a white pyroxene, a pale-green serpentine, and a dark-green alumino-magnesian mineral, which is allied in composition to chlorite and to pyrosclerite, and which I have referred to loganite. The calcareous septa in the last case are found to be dolomitic, but