430 PROCEEDINGS OF THE AMERICAN ACADEMY. 



In May, 1898, small sheets of native copper were seen by the writer 

 in vein matter coming up from the deep levels, but have not yet been 

 observed in the standing vein. The matrix is a light yellow densely 

 granular mineral with resinous lustre, which appears from jJi'eliminary 

 tests to be a phase of the yellow manganese garnet (polyadelphite) 

 so common in the vein matter of the Parker shaft. It is intimately 

 mixed in microscopic veinlets and larger masses with an amorphous 

 (often e;irthy) light pink manganese mineral not further identified. 

 A thin section of this gangue shows cloudy yellow spots of the garnet 

 surrounded by paler transparent material which has the feeble double 

 refraction in sectors of some garnet, a property which has not been 

 observed by the writer in the ordinary deep yellow garnet of the ore 

 body. This abnormal character and the veining by the pink material 

 suggest an alteration of the original garnet gangue with which the 

 deposition of the copper might have been contemporaneous. 



Mr. Van Mater states that native copper occurred in 1897 about 

 eight hundred feet below the surface in a seam in the middle of the ore 

 body, i. e. about half way between the hanging and foot walls. This seam 

 was filled with a gangue of rhodonite and other minerals in an earthy 

 porous condition, and probably represents the form just described. 



The other occurrence in massive willeraite was not observed in the 

 standing vein, but was jDicked out from the ore coming from about the 

 same depth. 



It is evident, from the relations of the veinlets of the copper to the 

 cleavage and cracking of the willemite and secondary pressure planes 

 of the calcite, that its deposition took place after the formation of the 

 zinc ores and associated minerals, and that possibly the circulation of the 

 solutions from which it was deposited took place along the same motion 

 planes in the ore body which produced the beautiful slickensides found 

 occasionally in this part of the deposit. There are no facts on which 

 to base a conclusion as to the form in which the copper was carried in 

 solution, nor as to the method of its final reduction and deposition, 

 although it is probable the changes noticed above in the garnet gangue 

 were connected with it. 



This occurrence increases the long list of minerals found at Franklin 

 Furnace and vicinity (now nearly seventy), and is an interesting addition 

 to the occurrences of native copper below the zone of surface oxidation. 



