604 GEOLOGY AND MINING INDUSTRY OP LEADVILLE. 



stamp mills, while the gritty particles fell to the bottom. By pouring off tlie sus- 

 pended matter, allowing to settle, decanting the supernatant liquid, and drying the 

 slimy deposit, an apparently pure matter was obtained, showing the pearly luster of 

 the original mass, and containing, like that, when air dried, about one-quarter of 1 

 per cent, of hygroscopic moisture. This is not included in the above analysis. No 

 further loss occurred ou prolonged heating until a temperature considerably above 

 lOOO C. was reached, while a strong red heat was requisite for complete expulsion of 

 the water. 



No altogether satisfactory formula can be deduced from the tigures in the table. 

 Ou dividing the molecular value by that for water, as being most accurately deter- 

 mined, the ratio is found to be 



gi02 : AI2O3 : E2(R)0 : HjO 



9,93 -1.09 1.87 3.00 



or, approximately, 



10 : 4 : 2 : 3. 



As no other specimens of a similar nature, from the Amie or other mines, have 

 been observed, by analysis of which it could be ascertained whether the above ratio 

 remains constant or not, it would be rash to aftirm that the material analyzed repre- 

 sents a distinct mineral species, the final i)roduct of the alteration of the porphyry 

 from which it is derived. 



No. 2, pure white, veined with manganese dioxide ; compact, hardness about 2, 

 rubbing off on the fingers when dry. When fresh and moist, frequently greenish in 

 color, o])aline in appearance, and semi-transparent, especially ou the thin edges, becom- 

 ing opaque on exposure. Insoluble in hydrochloric acid. Portions free from MnOj 

 taken for analysis. 



It was found that after two or three years' exposure to the air a large amount 

 of water, 3.36 per cent, of that given in the analysis, was still retained in a very weak 

 state of combination, apparently as hygroscopic moisture, since it escaped over sul- 

 phuric acid. No further loss occurred on heating at 100° C, nor below 100° C. to 170° 

 C, although blackening took place, due to carbonization of organic matter. Dried 

 over sulphuric acid or at 100° C, the powder was so extremely hygroscopic that it was 

 deemed advisable to make the analysis upon air dried material. The percentage of 

 loosely combined or hygroscopic water was found to decrease slowly on long exposure 

 of lumps to the air, so slowly as to be perceptible only at intervals of a month or more. 

 Deducting all water driven off at 100° C, the molecular ratio SiO. : AI2O3 : H2O is 

 1.98 : 1.00 : 2.20, thus showing the substance to be closely allied to kaoliuite.' 



Nos. 3, 4, and 5. In general appearance 4 and 5 differ little from the substance 

 last described. Color, white, streaked frequently with iron and manganese oxides; 

 hardness, after long exposure, in case of 5, about 2i. Practically insoluble in hydro- 

 chloric acid. No. 3 is pure white, and resembles 1 ; it contained no hygroscopic water. 

 No. 4 contained but 1.23 per cent. ; while No. 5 retained 4.5S per cent, of the same 

 (included in the analysis), after long exposure to the air in the form of lumps. 



'The same is foand in the Morning Star consolidated group of mines according to L. D. Rickette, 

 one of whose published analyses (The Ores of Leadville, Princeton, 1883) shows a ratio SiOa : AlgO, : 

 HjO = 2 : 1 : 3, prohably iuehidiug hygroscopic or weakly combined water. 



