W. P. Headden — Stannite, etc. 105 



Art. XIV. — Stannite and some of its Alteration Products 

 from the Black Hills, S. I). ; by ¥m. P. Headden. 



Several years ago Mr. Fred. J. Cross found at the Peerless 

 Mine, which is located about one-half mile northeast of the 

 Etta Mine post office, and was then being worked for mica, a 

 piece of some mineral imbedded in the pellucid quartz of the 

 locality which he did not recognize as having seen before 

 either from this or any other locality in the Hills. This mate- 

 rial which he kindly gave me forms the subject of this investi- 

 gation. One piece was all that Mr. Cross found at the time 

 and, though he has subsequently sought for it diligently, he 

 has been unable to find more of it, and 1 have been entirely 

 unsuccessful in my search for it ; therefore the description of 

 the occurrence of this mineral in the Black Hills must be con- 

 fined to the description of this one specimen with such excep- 

 tion as will be mentioned hereafter. 



The exterior of the mass is earthy in texture and from dirty 

 green to brownish yellow in color. The texture and color 

 change rapidly the former becoming in the interior firm, 

 almost massive, with uneven to subconchoidal fracture, while 

 the color passes through a pure copper-green to greenish black. 

 The appearance of the mass leaves no doubt but that it is 

 what remains of an original mass now in an advanced stage of 

 alteration. This is plain to the naked eye, but is best seen 

 under a good pocket magnifier. The texture of the mass 

 varies, even in those portions which are earthy, and where the 

 alteration is most complete there are portions varying in size 

 from mere points to particles as large as small shot which have 

 a vitreous luster, a green color, and an uneven fracture which 

 is rather difficult to observe. A closer study of these spots 

 shows that they, like the mass itself, are filled with seams and 

 are only remnants of an unrecognized decomposition product. 

 While these particles are readily distinguishable from the 

 enveloping mass, they are so permeated by seams filled with 

 other material, probably identical with the mass itself, that no 

 mechanical separation of the two would be possible. The 

 dull earthy substance becomes less abundant in the interior 

 but is nowhere absent. 



The portion having a copper-green color is similar to the 

 lustrous spots of the other portion and the two are probably 

 identical. The former like the latter is traversed by a fine 

 network of seams whose centers are filled with a substance 

 appearing to be almost white when viewed with a rather strong 

 magnifier. This is particularly easily observed in the larger 



