BESCRIPTIOil OF THK IPOPHYLLITEl. §73 



elopipedon, having a triple tendency to exfoliation, by ^re^ 

 by acids, and by friction *. 



Physical char. Specific gravity 2*467. 



Hardness: not scratching glass, and giving no sparks 

 ^vith steel : scratching fluate of lime feebly, and carbonate 

 of lime very evidently. If a fragment be rubbed sidewise 

 on a hard substance, as if to polish it, it splits into leaves. 



Refra^ction, simple. 



Electricity, easily excited by friction. It is the vitreous. 



Lustre. The surface of the crystals has a mean lustre 

 between glassy and pearly, united with a transpdrency iti 

 general decided, without any proper colour. 



Fracture, conchoidal, moderately shining. 



Geometrical characters. Its primitive form, PI, VII, fig. 3, 

 is a quadrangular right prism with rectangular bases. The 

 divisions parallel to M are very clear, and easily obtained. 

 Those answering to P and T are not very evident except iri 

 a strong light f. 



Chemical characters. Exposed to the flame of a candle, 

 it splits into leaves. Before the blowpipe it fu,ses with dif- 

 ficulty into a white enamel. Immersed in cold nitric acid 

 it divides in a few hours into small fragments, which at 

 length become a white flocculent matter. Its powder fornix 

 in it a kind of jelly, similar to that produced under the 

 same circumstances by the mesotype, or zeolite. 



Analyses of the apophyllite. 

 By Riiimaii, Fourci-oy and Valiqitelln, ItoSi*; 



Silex.....'...55 51 ...55 Cbmpot,ent 



Lime ..r....27 28.. *.,.., ,35 paru. 



Magnesia- •• • 0*5 



Potash •4 « 2-25 



Alumine 2*5 



Water 1? 1? "15 



102 100 , 97-25 



* From this character I liaVe takdii the name cf apophyllite, signi- 

 fying, " a stone that e«foliates," 



f The proportions of tlie three dim€nsi(»ns C, G, Bj are those of th« 

 numbers V 8, -/ 9, V 13. 



Vol. XXVII— Dec. ISIO. T The 



