356 J. Stansfield — 



Banded Precipitates of Vivianite in a 

 Saskatchewan Fireclay. 



By J. Stansfield, M.A., F.G.S. 



(By permission of the Director of the Geological Survey of Canada.) 



(PLATE XVI.) 



WHEN visitijQg the fireclay quarry of the Dominion Fire Brick 

 and Clay Products Company at Claybank, Sask., during the 

 summer of 1918, the writer noticed an occurrence of banded pre- 

 cipitates in the fireclay of one part of the quarry. Through the kind- 

 ness and courtesy of Mr. H. G. Love, Managing Director of the 

 Company, a collection of some examples of the occurrence was made 

 and forwarded to the writer for further examination. 



The fireclay worked by the Dominion Fire Brick and Clay Products 

 Company is exposed on the slope of the escarpment of the Missouri 

 coteau, which, at Claybank, is facing north, though generally the 

 coteau faces north-east. Usually, the coteau is covered with drift 

 deposits, and Claybank is one of the few points along it at which 

 the Tertiary strata to which the fireclay belongs are exposed. The 

 fireclay has been described in the reports of the Geological Survey 

 of Canada, and also of the Mines Branch, Department of Mines. ^ 



In the qaarry the fireclay has a light grey colour. At the northern 

 part of the floor of the quarry, as exposed during the summer of 

 1918, some bluish-black spots of circular or elliptical outline were 

 noticed, which are the subject of this paper. 



The stained parts of the clay are sometimes spherical in outline, 

 sometimes ellipsoidal, and often elongated so as to approach the 

 cylindrical, with rounded ends. The stains vary in diameter from 

 I in. to 1| in., less than | in. in diameter being usual. The greatest 

 length of axis noticed in a cylindrical case is one inch, but only part 

 of the whole specimen was available. 



The bluish-black stain is deepest in colour at the centre of the 

 sphere, or along the axis of the cylinder. Around the central stain 

 there may be a non-banded stain of less intense colour, or there may 

 be one, two, or three separate concentric stains of similar kind, but 

 not quite so dark in colour as the central stain. In true cross-sections 

 these stains have an approximately circular outline (see Fig. 1 centre), 

 though in some cases the circle may not be complete (see Fig. 1 

 upper left). Inclined sections of the cylindrical examples show 

 elliptical shapes (Fig. 1, top, middle ; Fig. 2, bottom, left and right), 

 and longitudmal sections of the latter show parallel lines on each 

 side of the axis. 



The clay between the bands may have the same colour as the 

 normal clay, or it may have a slightly darker colour, owing to the 

 presence of a small amount of the pigmenting material (Fig. 1, 



1 Ries & Keele, Mem. 2iE Geol. Sun. Can., 1912, pp. 84-92. Davis, N. B., 

 Report on the Clay Besources of Southern Saskatchewan, 1918, pp. 66-71. 



