20 The Rev. S. Haughton's Notes on Mineralogy, 



holding silica in solution, as we know it to be capable of doing 

 to a very great extent. 



In whatever point of view we regard this mineral, it must be 

 considered one of great interest, in consequence of its being a 

 hydratcd aluminous silicate, without protoxide bases, and con- 

 taining a proportion of silica to alumina the same as that found 

 in ortlioclase. I am of opinion that it is a new mineral species, 

 and I woidd propose to call it Hunterite, in honour of one of the 

 gentlemen who brought it to England. If we neglect the lime 

 and magnesia, it may be regarded as having the following mi- 

 neralogical formula, — 



5[A12 03, 3Si03 + 3HO] + [HO, 3S103]; . . (II.) 

 being, in fact, composed of five atoms of a hydrated tcrsillcate of 

 alumina* combined with one atom of a hyaline silica of admitted 

 composition. It appears to me to be a confirmation of this view 

 of the mineral, that in the gneiss that accompanies the granite 

 of Nagpur, and is often undistlnguishable from it, this fatty fel- 

 spar often passes into yellow and pinkish opalescent minerals, 

 with which it evidently has the closest relation. 



If we take account of all the elements present, and adopt 

 Scheerer's view of the replacement of magnesia by three atoms 

 of water, we find the following, which is exact : — 



403 [AFO^ 3Si03+H0] +356r32o}sioO +215IIO; 



or, approximately, 



4[2(AF03,3Si08) + 3H0]+5[3^Q|si03j. . (III.) 



Whatever view be adopted as to the rational formula of this 

 mineral, it is certain that part of its silica is in chemical com- 

 bination with water ; and if it be regarded as a metamorphic 

 orthoclase, it is to be considered as one from which only -/guds 

 of the silica has been removed, and that the potash has been 

 chemically replaced by water. 



No. 10. Gneiss formed from the preceding granite, composed of — 



1, Watery quartz. 



2. Pink, white, and yellow opaline felspar, with a waxy 



lustre. 



Locality : Nagpur City. 

 No. 11. Fine-grained granite, composed of — 



1. Quartz. 



2. White felspar. 



3. White mica in lozenges. 



4. Small crystals of garnet (abundant). 

 Locality : Korhadi. 



* In fact, an aluminous Glaueonite. 



