On the Nature of Louisite. — By Prof. T. L. Walker, 

 Ph. D., Director of the Royal Ontario Museum of Miner- 

 alogy, Toronto, Ontario. 



(Read 16 April, l^'^.^) 



In 1878, Honeyman, Nova Scotian Institute of Natural 

 Science, Vol. V, p. 15, gave this name to a zeolite which 

 formed part of a boulder picked up on the Blomidon shore, 

 King's County, Nova Scotia, by Mr. Robert \V. Starr, who 

 accompanied Dr. D. Honeyman while he was engaged in July, 

 1877, in the study of the geology of that region. It was analyzed 

 by Henry Louis, then of Londonderry Mines, N. S., after whom 

 it was named by Dr. Honeyman. The mineral was closely 

 related to apophyllite in composition except that it was much 

 higher in silica. 



The type specimen is the property of the Provincial Museum 

 in Halifax, and when Mr. Harry Piers, curator of that institu- 

 tion, suggested that it should be re-examined, I gladly accepted 

 in order to find the true place of louisite among the zeolites. 



The specimen, which is waterworn, weighed less than one 

 pound. It is white on the outer surface, and when examined 

 by a strong lens is seen to contain innumerable tiny roundish 

 masses somewhat glassy in lustre. The white crust extends to 

 a depth of about an eighth of an inch and surrounds the leek- 

 green glassy mineral which has been known as louisite. Louisite 

 is quite cleavable in one direction, possesses a vitreous lustre, 

 and as it can be readily scratched with a knife, appears to be 

 about 5 in the scale of hardness. Its streak is white, and accord- 

 ing to Louis it has a density of 2.41. 



A thin section prepared for microscopic study showed 

 when examined between crossed nicols that louisite is an aggre- 

 gate of radiating spherules of quartz in cleavable apophyllite. 

 (Figure 1). A portion from the centre of the mass was crushed 

 and treated with a heavy liquid consisting of bromoform and 

 carbon tetrachloride of such a density that about half of the 

 powdered mineral floated, while the rest sank to the bottom. 



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