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XXVI. Description and Analysis of some Minerals. By THOMAS 

 THOMSON, M. D., F. R. S. L. & Ed. &c., Professor of Che- 

 mistry, Glasgow. 



(Read 21 st April 1828.) 



1 . Anhydrous Silicate of Iron. 



J. HIS mineral was given me for examination by PATRICK 

 DORAN, an Irish mineral-dealer, who discovered it in Slavcorrach, 

 one of the Morne Mountains, on the north-east coast of Ireland, 

 forming so conspicuous an object at the southern extremity of 



the county of Down. 



j 



The colour is dark brown, with something of the metallic 

 lustre. 



The mineral is foliated, and breaks easily into four-sided 

 prisms, seemingly right ; though the summits are very obscure. 



The fragments are strongly attracted by the magnet, but 

 they have no poles. 



Hardness 4. 



Opaque. 



Easily frangible. 



Specific gravity 3.8846. 



When heated in a glass-tube, it gives out ammoniacal va- 

 pours, and loses 1.97 per cent, of its weight. 



Infusible per se before the blowpipe, but in the reducing 

 flame acquires the metallic lustre, and assumes very much the 

 appearance of magnetic iron-ore. 



In muriatic acid it dissolves by the assistance of heat, without 

 effervescence, leaving behind a quantity of silica in fine flocks, 



