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LXIII. On Collyrite, and a native Carbonate of Alumina and 

 Lime. By J. H. Gladstone, Ph.D., F.R.S., and G. 

 Gladstone, F.C.S* 



AT Hove, near Brighton, is an old quarry in the upper chalk 

 that presents some appearances of more than ordinary inter- 

 est. Among these are the faults which have traversed the strata 

 and broken the layers of flint, splitting them in every direction, 

 and reducing them in some places almost to powder. Some of 

 these fissures are filled up with a mineral whiter than the sur- 

 rounding chalk, and perfectly distinct from it, which runs also 

 along the dislocated layers of flint, and frequently imbeds the 

 fragments. 



This very white mineral occurs in rounded masses easily dis- 

 integrated in water. It is very soft, easily friable, with an earthy 

 fracture, of low specific gravity, porous, and slightly hygroscopic. 

 The external portions are frequently stained red with sesquioxide 

 of iron. When examined chemically, it was found to consist 

 mainly of hydrated silicate of alumina, perfectly decomposable 

 by strong hydrochloric acid. There was also a varying amount 

 of carbonic acid and of lime. The alumina was found to be free 

 from phosphoric acid ; nor was it mixed with glucina, a small 

 quantity of which has been recently found so often to accompany 

 this earth. The mineral, when strongly heated, gave off both 

 the combined water and the carbonic acid. 



For analysis the mineral was pounded and allowed to stand 

 over sulphuric acid in vacuo till freed from all hygroscopic 

 moisture. The determination of the different constituents was 

 made in the usual manner. 



A very soft, pure-looking specimen gave the following pro- 

 portions : — 



Silicic acid 14-49 



Alumina 47*44 



Carbonic acid .... 0*79 



Lime 0*89 



Water and loss . . . 36*39 



100-00 



The carbonic acid and lime, being in very nearly equivalent pro- 

 portions, may be assumed to have existed in combination ; and as 

 they form together only 1*68 per cent., they may be considered 

 as no constituent part of the aluminous mineral. 



Excluding them, the results of analysis are as given below 



* Communicated by the Authors. 



