Abstract
Mr. W. H. Penning, F.G.S., examined a certain rock near Lydenburg, when in company with Mr. A. C. Crutwell, and they described it in the Quart. Journ. Geol. Soc. vol. xli. (1885) p. 576, as “a peculiar blue, fine-grained, calcareo-siliceous rock.” This they named “‘chalcedolite,’ in consequence of the chalcedonic texture frequently displayed-indeed, some portions of the rock are true chalcedony.. . Sometimes it occurs in amorphous masses, weathered to a grey colour, and to a peculiar, rough, trachyte-like surface; but mostly in thin beds, 2 or 3 inches in thickness, with earthy partings.” Mr Penning in another contribution, Quart. Journ. Geol. Soc. vol. xlvii (1891) p. 456, mentions the same rock (chalcedolite) as immediately overlying the ‘Black Reef series’ of what he calls the Megaliesberg Beds.’ Mr. C. J. Alford, F.G.S., in his ‘Geological Features of the Transvaal,’, mentions the occurrence and peculiarities of this rock as follows:- Page 3. Referring to ‘alluvial deposits,’ he states:“In several places deposits of a fairly pure crystallite carbonate of lime are met with, those in the vicinity of the Six-mile Spruit, between Pretoria and Johannesburg, being some of the most remarkable; these appear to result from the disintegration of a hard blue quartzite plentifully veined Page 6. “The metamorphism of these beds[‘schistose rocks’], where in contact with, or ajdacent to, the irruptive rocks, results in several somewhat complicated products; amongst others the calcareous quartzite before mentioned, which in some places passes into dolomite, and on exposure to atmospheric influence yields up its
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call