OEES AND VEIN MATERIALS. 



'603 



brown hydrated ferric oxide, the boundaries beiug iu places rather sharply defined, in 

 others indistinct. The dark zone was iii turn surrounded by a zone of light-brown 

 oxide, the Hue of demarcation being very regular and sharply defined. The dark oxide 

 was compact and flinty; the light oxide also compact, but less hard. 



TABLE XI. Alteration products of porphyry. 



a Includes 0.23 PjOj. 



6 By difference. 



c Present as a visible imparity. 



Amie mine, in ore body. Ore Coll. No. 55b. 



New Discovery mine. Ore Coll. No. 55a. 



Big Pittsburgh, contact of Gray Porphyry. Ore Coll. No. 56b. 



Morning Star mine. Ore Coll. No. 56. 



Swamp Angel tunnel, contact of White Porphyry. Ore Coll. No. 5fib. 



Lower Waterloo mine. Ore Coll. No. 105a. 



Lower Waterloo mine. Ore Coll. No. 105a. 



Lower Waterloo mine. Ore Coll. No. lOob. 



REMARKS ON TABLE XI. 



Owing to the indefinite nature of the greater part of the peculiar products of 

 alteration represented by analysis in the above table, it is impossible to ascribe to them 

 distinctive names. Notwithstanding the great external similarity of all but the first 

 of the specimens examined, they have been found to differ most widely in composi- 

 tion, though, aside from the above exception, three distinct groups may be recognized, 

 namely: First, simple hydrated aluminium silicates allied to kaoliuite; second, mixed 

 aluminium silicates and aluminium and alkali sulphates, likewise hydrated; and, third, 

 certain hydrated aluminium and zinc silicates, also mixtures. 



In the following are given the distinctive physical and chemical characteristics, 

 accompanied by brief discussions of the analytical results : 



No. 1, grayish white ; compact, but of hardness considerably less than 1, rubbing 

 off on the 'fingers ; luster, pearly; iusoluhle iu hydrochloric acid. Evidently derived 

 directly from porphyry, since honeycombed remnants of feldspar crystals, and even 

 large crystals, an inch in length, showing rough faces, occur imbedded in the mass. 

 Under the microscope it appears to consist of crystalline scales without definite form. 



In order to obtain material for analysis free from uudecomposed feldspar, it was 

 slightly crushed and stirred with water in a beaker, whereby it became thoroughly dis- 

 integrated, the fine matter floating and imparting to the water a beautiful satiny 

 appearance similar to that frequently observable in streams receiving the tailings from 



