ORES AND VEIN MATEKIALS. 



603 



browL liyclrated ferric oxide, the bouiularies beiug iu places ratber sharply defined, iu 

 others iiulistiuct. The dark zoue was iu turn surroiiuded by a zoue of lightbrowu 

 oxide, the Hue of demarcatiou beiug very regular aud sharply defined. The dark oxide 

 was compact aud fliuty; the light oxide also compact, but less hard. 



Table XI. — Alteration products of porphyry. 



105a 

 lOSa 

 105b 



34.01 

 37.78 

 35.60 



0.56 

 2.26 

 0.03 0.77 



FeO 



33.05 

 35.40 

 18.43 



0.22 

 Trace 



0.23 

 0.53 



1.62 

 1.87 

 0.63 



l.ll 



0.30 



Trace 



0.30 

 1.14 



9.88 I 0.67 



Trace 

 2. 73 5. 26 



4.42 

 17.95 

 15.05 



1. 30 16. 67 

 1. 56 616. 51 



19.06 

 17. 4G 

 16.37 



Trace 



34.55 



100.03 

 99.91 [ 

 100. 00 



15.48 101.1511 

 13.75 100.00 ' 



100. 15 

 100. 31 

 100. 10 



a Includes 0.23 PsOb. 



bBy difference. 



: Present as a visible impurity. 



Amic 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. 5G. 



Swamp Angel tunnel, contact of White Porphyry. Ore Coll. No. 56b. 

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

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

 , Lower Waterloo mine. Ore Coll. No. 105b. 



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 

 di.stinctive uames. Notwithstanding the great exterual similarity of all but the first 

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

 tion, though, aside from the above excei^tiou, three distinct groujis may be recognized, 

 namely: First, simi)le hydrated aluminium sili:?ates allied to kaolinite; second, mixed 

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

 certain hydrated aluminium aud 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 harduess considerably less than 1, rubbing 

 ofl' on the fingers; luster, pearly ; insoluble iu hydrochloric acid. Evidently derived 

 directly from porphyry, since lioneycombed remnants of feklspar crystals, aud 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 undecompo.sed feldspar, it was 

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

 integrated, the fine matter floating aud im])arting to the water a beautiful satiny 

 api)earance similar to that frequently observable iu streams receiviug the tailings from 



