1 50 Intelligence and Miscellaneous Articles. 



If we consider, with M. Frankenheim, Cu s S to be isomorphous 

 with ZnS and FeS, the following simple formula results : — 



Copper blende essentially differs from tennantite in having a por- 

 tion of Cu a S replaced by Zn S. — Poggendorff's Annalen. 



BommjsB i 



LOXOCLASE (FELSITES L0X0CLASIUS\ A NEW MEMBER OF THE 

 FELSITE GENUS. BY A. BREITHAUPT. 



Amongst a number of North American minerals, for which I have 

 to thank Mr. Shepard, were several of the genus Felsite, and one in 

 particular which at first sight I took for pegmatolith, but which turns 

 out to be a new and remarkable species. This mineral in many 

 respects resembles oligoclase : I have therefore, in the following de- 

 scription, pointed out those peculiarities which render it distinct. 

 Lustre, between vitreous and greasy; pearly on the most perfect 

 cleavage-surface. 



Orthoclastic. — Primary form, oblique rhombic prism, 4-Poo"(P) 

 = 63° 38' towards the chief axis ; -P»W = 65° 37' towards the 

 chief axis; P :y=3tf= 99° 45'; P :T= 112° 30' ; P : /= 112° 50' ; 

 P : M = 90° 0' (oligoclase P : M = 86° 45') ; M : T = 120° 15' ; 

 M : / == 119° 25' ; T : / = 120° 20'. Cleavage, perfect hemidomatic ; 

 very distinct in the direction of the short diagonal ; indistinct ap- 

 proaching distinctness in the direction of the long diagonal ; hemi- 

 prismatic, in fragments. Fracture, uneven to conchoidal and hackly. 

 Hardness = 1\ to 7£ (of Breithaupt's scale) (oligoclase 7| to 8|). 

 Specific gravity = 2*609 to 2-620 (oligoclase 2-644 to 2-662). 

 Colour, yellowish-gray, yellowish-white, pea yellow, bluish-gray. 

 Translucent in thin laminae to transparent. The oblique cleavage 

 in the direction of the long diagonal is characteristic of loxoclase, 

 although not always very distinct, hence its name. Its specific 

 gravity is also higher than any other of the orthoclastic felsites. It 

 appears subject to decay by exposure to the atmosphere. 



Two analyses performed by Prof. Plattner ; the one by means of 

 hydrofluoric acid (a), the other by carbonate of soda (b) ; the mean 

 of the two (c) showed it to possess the following composition :— 



binca . . . . .^ . ^ . . . jflfc.flft-v j, HS pa 03 50 63 50 



Alumina 20"48 20*10 20-29 



Oxide of iron 065 0-70 0*67 



Potash 3-03 3-03 



Soda 8-76 8-76 



Lime 3-40 304 3-22 



Magnesia trace trace 



Water and fluoride of silicon . . 1-23 T23 



for which the general formula is RO, S0 3 + R 2 3 , (SO,) 2 , as also 

 for oligoclase. Loxoclase affords therefore a remarkable example of 



