Mineralogical Notices^ 25 



OCCURRENCE OF ARSENIC IN IKON PYRITES. 

 BY M. BREITHAUPT. 

 [PoggendorfF's Jnnalen^ vol. Ixxvii. p. 141.]; ,, -fnt 

 Breithaupt has examined a vast number of iroii pyrites for,,, 

 arsenic, which metal he finds to be most extensively diffused, 

 forming in general from i — 1 per cent. It is probable that 

 all the iron pyrites upon heavy spar and fluor spar contain 

 arsenic. ,. 



GLAUCOLITE. BY M. GIWARTOWSKI. 

 {Joum.furPrakt. Chem., vol. xlvii. p. 380.}''\'' " - 

 This mineral is found at Baikal; it is imbedded in and pe- 

 netrated by a greenish-yellow mica, has a blue colour varying 

 from light to indigo blue, is transparent at the edges, has 

 nearly the hardness of felspar, and a crystalline granular frac- 

 ture. Its powder is white with a faint tint of lilac, which dis-' 

 appears on ignition ; spec. grav. at 62° '■2'65. According to 

 the following analysis by Giwartowski, it has the formula 

 RO, SiO^ + Al'^O^, SiCF. For comparison, the former analyses 

 by Bergmann and Jahn are added : — 



Giwartowski. Bergmann. Jahn. 



Silica 50-4.94 50-583 25*50 



Alumina 28-125 27600 16-00 



Lime 11-309 10-266 2*00 



Magnesia ...... 2678 3-733 



Soda 3-103 2-966 



Potash 1-006 1-266 



Protoxide of manganese . . 0-595 0-8661 „_ 

 Protoxide of iron .... 0-397 I'lOOJ 



Water 1-786 0-733 1 



Lqs«,:% 0-407 0-887/ ^"" 



baufol- 100-000 100-000 50-QQ-.jfq 

 ^^iii' Aivnn 



\. ARKANSITE AND BROOKITE, BY M. RAMMELSBERG. '"-^^'1 

 [Poggendorff's Aimalen, vol. Ixxvii. p. 586.] t7 



According to the researches of Rammelsberg, Arkansite is 

 only a variety of Brookite. Arkansite was discovered by Powell 

 at Magnet Cove, Hot Springs, County Arkansas, and de- 

 scribed and named by Shephard. According to him, this mi- 

 neral, when heated in a glass tube, furnishes neither moisture 

 nor hydrofluoric acid ; it is not changed before the blowpipe, 

 and gives a dark yellow glass with borax. When boiled with sul- 

 phuric acid, it is converted into a yellowish-green mass, which 



