Chemistry — Mineralogy. 373 



tut also the rest of the characters of the two kinds of Uranite have not hi- 

 therto presented any decisive mark by which they might be distinguished 

 with perfect security; but it must be allowed that the substances them- 

 selves are very imperfectly known. When these, particularly the variety 

 from Autun, shall have been more accurately examined, it will be possible 

 to say whether or not they should form separate species, for nothing can 

 follow from the isomorphism of two bodies upon the determination of the 

 species ; since Berzelius himself, who derives the specific difference of 

 Chalcolite and Uranite from the presence of two isoraorphous bases, consi- 

 ders the presence of arsenic acid, in greater or smaller proportions in the 

 Chalcolite, as unavailing, because this and the phosphoric acid are iso- 

 morphous bodies. (Poggendorff's Ann. der Phys. 1824. 8. p. 379.) 



III. NATURAL HISTORY. 



MINERALOGY. 



26. Axotomous Arsenical-pyrites, a New Mineral Species. 



Prismatic. P = 117° 28', 90° 51', 121° 58'. Approx. 

 (a : b : c = 1 : ^0.8747 : ^0-4806.) 



Simple forms. Pr (o) = 51° 20' ; P + cc (d) = 122° 26'. 



Combination. Pr P + a>. Fig. 13. Cleavage, P — cc, perfect; less 

 distinct Pr = 86° 10'; traces of P + cc. Fracture uneven. Surface faintly 

 streaked parallel to the common edges of combination, frequently smooth. 



Lustre metallic. Colour between silver-white and steel-grey. Streak 

 greyish-black. 



Brittle. Hardness = 5.0 . . . 5.5. Sp. Gr. = 7.228, the massive va- 

 riety from Reichenstein. 



Compound varieties. Massive : composition granular, individuals small, 

 often nearly impalpable, and strongly connected, fracture uneven ; composi- 

 tion columnar, rather thick and irregular, and divergent. Faces of composi- 

 tion irregularly streaked. 



Observations. — The axotomous arsenical-pyrites contains arsenic and 

 iron, in proportions which have not yet been ascertained. It occurs in a 

 bed of sparry iron, at Loling, near Hiittenberg, in Carinthia, along with 

 octahedral bismuth and skorodite, and was distinguished by Professor 

 Mohs from the other more common species of arsenical-pyrites. The 

 same species he found afterwards among the cobalt ores from Schlad- 

 ming, in Stiria, and imbedded in the serpentine from Reichenstein, 

 in Silesia. In the latter place it seems to occur in very considerable 

 quantities. The crystals have been observed among the varieties from 

 Schladming. (Mohs, vol. ii. p. 522. Trans I. vol. ii. p. 448.) 



27- Prismatoidal Copper-Glance, a New Mineral Species. 



Prismatic. Combination. 1. Pr (P) P + cc . (M ) Pr + co" (A). 

 Sim. Fig. 11. Cleavage, Pr + * rather perfect, though interrupted. 

 Fracture imperfect conchoidal. Surface rough. Lustre metallic. Colour 

 blackish lead-grey. Streak unchanged. Brittle. Hardness = 3.0. Sp. 

 Gr. = 5.735. 



