V. Note on a Specimen of Altered Dolomitic Limestone from the Cement-Stone Series of the Ballagan Group

Abstract

Last summer Mr. John Young drew my attention to specimens of a peculiar-looking rock found by Mr. Alexander Buchanan at Fintry. The specimens were of a uniform light-chocolate-brown colour and apparently perfectly homogeneous. They were somewhat harder than common limestone, had a waxy lustre, and broke with a sharp-edged splintery fracture, translucent upon the thin edges. With hydrochloric acid they effervesced slowly, at the same time gelatinizing. Externally the specimens were weathered white, and were traversed on the surface by deep fissures coated with a crust of carbonate of lime. Mr. Young and myself were led at first to believe that the specimens had been found in situ . We discovered subsequently, however, that they had been found detached, and not far from the site of an old lime-kiln. On looking to their analysis there is little doubt that they had actually passed through the kiln and had originally come from one of the beds of the Ballagan limestone in the neighbourhood. The difference in composition between the specimens exhibited and specimens of Ballagan limestone analysed by Mr. Young* is just what would be accounted for on this supposition. Although outwardly the specimens appeared homogeneous, analysis showed a considerable variation in composition, but by selecting portions taken from the centre of the mass and as nearly as possible uniform in colour, results which agreed fairly well with one another were obtained. Dried at 100° C. the speciments lost 8·7 per cent. of water. Analysis of the dried specimens gave the following This 250-word extract was created in the absence of an abstract