NATURAL SCIENCES OF PHILADELPHIA. 800 



By taking 2 Cii = Ag. we have the formula (Ag C u Fe) S or 6 Ag S +- 2 Cu 

 S + Fe S. 



POLYBASITE. 



I am indebted to Joseph A. Clay, Esq., also, for a duplicate specimen of an unde- 

 termined mineral, which he lately received from Peru, labelled "A compact silver 

 ore from San Pedro Nolasio, Tres Puntos, near Copiapo." From a fragment of 

 a crystal I made an approximative analysis, which proves the mineral to belong 

 to this species, as I have with the quantity at my disposal (0-0814 grammes,) 

 been able with care to determine the proportion of the sulphides of silver and 

 copper, which prove by the excess of base, that the mineral is of the species so 

 appropriately named Polybasite. 



The specimen which I have, contains short tabular hexagonal crystals, the 

 terminal planes of which show the triangular striae. These crystals are imbed- 

 ed in crystallized gypsum, and are more developed by keeping the specimen for 

 a short time in cold water. Calcite in scaleneohedrous crystals, minute portions 

 of blende and pyrites were also associated in the specimen. 



Hardness about 2. Lustre metallic : color between steel gray and iron black. 

 Streak, iron black. Opaque sectile, brittle, soft. Fracture uneven. 



The following are the results of my analyses : 



Per cent. Quotient. Ratio. 



Sulphur 16-14 1-0 8 



Silver 64-18 0-59 5 



Copper 8-13 0-26 2 



(Arsenic and Antimony) loss.. 11-55 0-12 1 



100-00 

 From which may be deduced the formula : 5 Ag S+Cu S-f-(As Sb) S 3 . 



Glascerite (?) 



In No. 1 of " Mineralogical Notes," published in the Proceedings of the 

 Academy of Natural Sciences for August, 1858, I mention a mineral which I 

 found among some specimens recently presented to the Academy, brought from 

 the Chincha Islands of the Pacific Ocean ; it was labelled " Ammonia."' From 

 its appearance I suspected it to be a sulphate. By a qualitative analysis the 

 sulphate of ammonia was found to be combined with a sulphate of one of the 

 fixed alkalies, which I then supposed to be principally soda. By a quantitative 

 analysis I now find that the quantity of soda is a minimum, and that the prin- 

 cipal alkali is potash. The salt is therefore really a double sulphate of potash 

 and ammonia, and notwithstanding the probability of its being a distinct salt 

 and a new mineral species, I will, for the present, refer it to Glascerite, with a 

 mark of interrogation. There is mentioned in Gmelin's Handbook of Chemis- 

 try, (Cavendish edition, vol. iii. p. 71.) a sulphate of potash and ammonia, which 

 from the description therein given, accords with this mineral, (" scaley, shining, 

 bitter crystals, unacted upon by the air and leaving neutral sulphate of potash 

 when ignited.") Not one analysis is given, neither is the proportion of potash 

 and ammonia mentioned, but reference is made to an article on this substance 

 (artificial double sulphate of potash and ammonia) by Link, Chemische An- 

 nalen von Dr. Lorenz Crell, 179, i, 29, to which work it is not in my power 

 to refer. 



The glascerite (?) is in compact lumps or concretions about the size of 

 hickory nuts ; the color is yellowish white, with a crystalline structure ; taste 

 pungent and bitter opaque ; permanent in the air. Hardness about 2. Reac- 

 tion with litmus paper perfectly neutral. Before the blow-pipe on platinum 

 foil, blackens and fuses with difficulty, leaving a white bead which is soluble 

 in water and tastes a little saline and bitter. When heated in a platinum cru- 

 cible it becomes first black and then burns perfectly snow-white, not fusing at a 

 high heat. 



1859.] 



