Riotte.] 216 [Mayl, 



The Pyroxene is in some cases of the variety Sahlite, and in some in- 

 stances Pargasite and Scapolite accompany the other named minerals. 

 At Amherst the crystals of Cinnamon Stone and Idocrase occur im- 

 bedded both in Limestone and Quartz, and it is noticeable that those 

 of the Quartz are much superior to the others. 



Dr. C. T. Jackson read the following description of a new 

 mineral, Stetefeldtite, by Mr. Eugene N. Riotte of Austin, 

 Nevada : — 



Allow me through your Society to make known to the scientific 

 world, a new mineral lately discovered by me, which I beg leave to 

 name '• Stetefeldtite." Specimens of the same will accompany this 

 paper. I would here return thanks to Messrs. Stoddar and Stetefeldt 

 for their aid in procuring in this wilderness, the following data, by 

 which I hope to be able to prove to your satisfaction, the existence 

 of a new species of mineral, the knowledge of the composition of 

 which, on account of its general occurrence in the southeast portion 

 of this State, and its great value in silver, will certainly be of great 

 importance to science and practice. 



The specimen sent and studied will be but one of a series in an or- 

 der of minerals, as for instance every specimen of fahlerz illustrates 

 but a subspecies of the tetraliedrite family. 



The extremes of this Stetefeldtite could be designated by the 

 formulas 



2 Cu'+Pv^O Sb= 0-'+6 HO 

 and 2 Ag'+Pt'O Sb- 0^+G HO. 



the chief diversity occurring as to the amount of silver. RO would 

 consist of variable quantities of Cu'O, feO and PbO, the latter sel- 

 dom. The most common mean would be a mineral containing about 

 one-half as much silver as the Ag' extreme. 



As extreme values for Ag', I have obtained from different localities 

 2 per cent, and 24 per cent., so that my notion of a species of mineral 

 is based upon investigation. 



Taking all these facts into consideration, I would describe it 

 mineralogically as follows : 



StetefekUUe. Massive, structure compact and even. H = 3.5 to 

 4.5. G. = 4.2. Limits 4.12 and 4.24 in four determinations. Lustre 

 dull slate like. Color, slate black, with an occasional blue and brown 

 tinge. Streak dirty yellow green. In the streak the mineral be- 

 comes shining, as also by rubbing with a hard substance. Fracture 

 uneven, sometimes conchoidal. Brittle to soft, only in the streak a 

 little malleable. 



