34*2 Dr Hartnian's Miiiei'alogical Notices. 



always recommended me to guarantee the maintenance of the 

 instruments in a state of good performance for a certain time, 

 such as twenty or thirty years, or indeed almost any limited 

 term, which recommendation I shall certainly follow, if suffi- 

 cient encouragement can be obtained for the establishment of 

 the manufacture. 



I am, Dear Sir, respectfully. 



Your most obedient servant, 



A. Blair. 

 Edinburgh, 16, Broughton Place, 

 3 J September 1827. 



Art. XXVII. — Mineralogical Notices, communicated by Dr 

 Charles Hartman of Blankenburg, of the Duke of 

 Brunswick's Mining Service, M. W. S. &c. &c. 



1. Gtlaucolite, a new mineral species. This substance was 

 first described by Mr SokolofFin the Russian Journal of Mines.* 

 It is found massive, presenting traces of cleavage. The frac- 

 ture is splintery and uneven ; lustre vitreous ; colour lavender- 

 blue, passing into green. It is translucent on the edges. 

 Hardness — 5.0... 6.0. Specific gravity = 2.721 Bergemann ; 

 = 2.9 John. 



According to Dr Bergemann, -f- it consists of 

 54.58 Silica, 4.57 Potash, 



29.77 Alumina, 11.08 Lime. 



Its mineralogical formula is NS^ + 3CS^ -f AS. 



Before the blowpipe it melts difficultly on the edges, but is 

 soluble in borax and salt of phosphorus. It loses it colour. 



It occurs in compact felspar and granular limestone, with 

 talc, near Lake Baikal, in Siberia. 



2. Bismuihic Blende, a new mineral species described by 

 Professor Breithaupt of Freiberg J.— Tessular. Simple forms. 

 Cl CI 

 2' 2 ' 2 * 



• Poggendorfi Annakn der Physik u. Chemie, 1827, Number ii. p. 267. 

 + Von Leonhard's Handbuch der Oi'yktognosie, 2d Edit. p. 741. 

 $ Poggendorfs Anmlen, ^c. 1827, Number ii. p. 275. 



