ORES AND VEIN MATERIALS. 605 



The air-dried material of 4 and 5 was analyzed, since, when dried over sulphuric 

 acid or at 100 0., the hygroscopicity was such as to render accurate weighing out of 

 the question. In very lew hours No. 5 reabsorbed, when exposed in the air, over half 

 of the 4.58 per cent, of moisture lost at 100 C. 



Consideration of the analyses, coupled with the observed insolubility in hydro- 

 chloric acid, shows beyond reasonable doubt that these bodies are mixtures of alunite, 

 K 2 SO 4 + ( A] 2 )S 3 Oi 2 +2H 6 (Al 2 )O 6 , corresponding in formula to the jarosite of the following 

 table, or of an allied mineral, with different indefinite hydrated aluminium-calcium- 

 magnesium silicates. If the supposed alunite is calculated on the basis of the sul- 

 phuric acid, the residual amounts of silica, alumina, lime, magnesia, alkalies, and 

 water are found to have widely different and not very definite molecular ratios iu each 

 analysis. 



From the fact of No. 3, which is mainly an aluminium-alkali sulphate, containing 

 no weakly combined or hygroscopic water, the hygroscopicity appears to be a prop- 

 erty of the hydrated aluminium silicates. 



Nos. 6, 7, and 8. Similar in appearance to the simple hydrated aluminium silicates 

 represented by analysis 2. Nos. 6 and 7 were taken by Mr. L. D. Eicketts from one 

 locality in the mine, No. 8 from another. The fiist and second were not to be distin- 

 guished from each other by the eye, being brilliantly white (greenish under certain 

 conditions of light), opaline and semi-transparent, while the third was veined with 

 iron and manganese oxides and possessed in a less degree the pronounced couchoidal 

 fracture of the others. On exposure they became opaque, and after some mouths 

 possessed a hardness of about 3. Nos. 6 and 7 were entirely and readily decomposed by 

 strong hydrochloric acid when finely pulverized, while upon 8 the action of the acid 

 was not so marked, though still energetic. The hygroscopicity of these substances, 

 especiall- of the first and second, is extraordinary. Over sulphuric acid No. 6 lost 

 11.64 per cent, of water, while No. 7 lost 10.26 and No. 8 but 5.30 per cent., these 

 amounts being included in the tabulated results of analysis. Exposure to a tempera- 

 ture of 100 C., and even 15C 0., occasioned no further loss in weight, but the presence 

 of organic matter made itself manifest by the blackening of the powder. The dried 

 material reabsorbed moisture with great rapidity. It was at first supposed that these 

 were, mixtures of calainine with some hydrated aluminium silicate. But if from the 

 molecular values those for zinc oxide are eliminated and proportionate amounts for 

 silica and water subtracted, on the supposition that calamine is present, the ratios 

 between the remaining molecular values are not the same as should be the case if the 

 mixture consisted in all these cases of calamine and one other definitely constituted 

 mineral. Moreover, on decomposing with hydrochloric acid no gelatinizatiou takes 

 place, and not even a trace of silica goes into solution, an argument against the pos- 

 sibility of the presence of either calainiue or willemite. The molecular values, con 

 sidered altogether for each analysis, do not present relations sufficiently definite to 

 allow of supposing any one of the specimens to represent a single mineral species. 



