ORES AND VEIN MATERIALS. 605 



The air-dried luateiial of 4 aud 5 was analyzed, since, when dried over sulpburic 

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

 the question. lu very Jew hours No. 5 reabsorbed, when exposed in the air, over half 

 of the 4.58 per cent, of moisture lost at lOQo 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, 

 K2SO4+ ( Al2)S30i,+2H6(Al2)06, corresponding in formula to the jarosite of the following 

 table, or of an allied mineral, with ditt'erent indeliDite hydrated aluminium-calcium- 

 magnesium silicates. If the sup|;osed 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 in each 

 analysis. 



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

 no weakly combined or hygroscoi)ic water, the bygroscopicity appears to be a prop- 

 erty of the hydrated aluminium silicates. 



Nos. C, 7, and S. Similar in appearance to the simple hydrated aluminium silicates 

 represented by analysis 2. Nos. 6 aud 7 were taken by Mr. L. D. Ricketts from one 

 locality in the mine, No. S from another. The liist aud second were not to be distin- 

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

 conditions of light), oi)aliue and semi-trausparent, while the third was veined with 

 iron and manganese oxides and posses.sed in a less degree the jironounced conchoidal 

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

 l)ossessed a hardness of about 3. Nos. G and 7 were entirely aud readily decomposed by 

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

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

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

 11.G4 per cent, of water, while No. 7 lost 10.2G aud 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° C, 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 calamine with some hydrated aluminium silicate. But if from the 

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

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

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

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

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

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

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

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

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



