(Table 3, page 309) Mercury content of concretions from Grand Lake (GL) and Ship Harbour Lake (SH), Nova Scotia and Mosque Lake (ML), Ontario

Ferromanganese concretions from Grand Lake and Ship Harbour Lake in Nova Scotia and Mosque Lake in Ontario are most common in water 0.5 to 2 m deep. X-ray diffraction studies show the ferromanganese portions of the concretions to he amorphous. Petrographic and electron probe studies of the ferromanganese material reveal chemical banding of iron and manganese. Bulk chemical analyses indicate that the Fe:Mn ratios of concretions from different sites within a single lake are similar, whereas concretions from different lakes have characteristic Fe:Mn ratios. Trace element concs are different in different lakes and are generally several orders of magnitude less than those of oceanic nodules.

(Table 1, page 605) Chemistry of concretions from Grand Lake (GL) and Ship Harbour Lake (SH), Nova Scotia and Mosque Lake (ML), Ontario

Studies by optical microscopy, x-ray diffraction, and electron probe techniques of ferromanganese concretions from three Canadian lakes reveal chemical banding of amorphous hydrated iron and manganese oxides. The average ratio of iron to manganese in concretions from these lakes varies from 0.43 to 2.56. The concentrations of cobalt, nickel, copper, and lead are one to two orders of magnitude below those reported for oceanic ferromanganese concretions.

(Table, page 500) Geochemistry of a pancake-shaped concretion from lake Charlotte, Canada

A pancake-shaped concretion from Ship Harbour Lake, a small freshwater lake in eastern Nova Scotia (now named Lake Charlotte) is part of collection sent to the National Museum of Canada by Mr. R. A. Logan, of the Pan American Airvays. These concretions are of similar to the well-known marine concretions with a composition similar to wad. These are known only from abyssmal depths of the sea in the red clay deposits, while the present concretions occur in very shallow lake waters. They should be of interest to geologists, who may be concerned with the rather difficult problem which some concretions raise of distinguishing between concretions of syngenitic and epigenetic origin.