ii. 208 ABSTRACTS OF CHEMICAL PAPERS. Miner a l o gi c a1 C h e mi s t r y. Pyrites and Marcasite. VIKTOR POSCHL (Zeitsch. Kryst. Min. 1911 48 572-618).-Descriptions are given of the surface characters of crystals of pyrites and marcasite as seen under a metallographic microscope. The characters of the faces and the form and orientation of the arti- ficially-produced etched figures suggest that the symmetry of pyrites is tetrahedral-pentagonal-dodecahedra1 rather than pentagonal-dodeca- hedral. Numerous determinations were made of the hardness of natural and of artificially-cut faces. The degree of hardness is assumed to be proportional to the volume of material removed (that is proportional t o the square of the width of the scratches produced) by a weighted diamond point moved across the surface.The hardness of pyrites relative to that of topaz = 1000 is 199.1 under a load of 50 grams and 182.2 under a load of 20 grams ; of marcasite 134.1 and 140.2 under the same loads respectively. On on0 and the same crystal no differ- ences in hardness were detected on different faces or along different directions on the same face. Different crystals however differ slightly in hardness and it is noticed that those which are softer are at the same time less dense. The specifically lightest and heaviest crystals of each lot experimented on were analysed with the following results but no essential differences are shown in chemical composition Fe. Ni. Go. Cu. I. 46.02 0'04 - 0.59 11. 46.19 0.07 - 0-63 111. 96-32 trace 0-06 0'09 IV. 46'18 trace 0'09 0,04 V.46-07 0'03 0'16 0'26 VI. 45'98 0'02 0.18 0.29 ++ Trace Ag. S. 51-70 51.55 51-78 51 '90 51-83 51.95 -t. Trace As. Total. Sp. gr. 0.93 99-28 5.098* 0.78 99-22 5.153" 1.52 99.77 5.078 1.73 99'94 5-113 1'28 99'63 5.068-f 1.19 99-61 5.lOlf. Mn. I and I I pentagonal-dodecahedra1 crystals (2lO} oE pyrites fromMINERALOGICAL CHEMISTRY. ii. 209 Elba ; I11 and IV ditto from Huttenberg Carinthia; V and VI ditto from Seegraben near Leoben Styria. L. J. S. Composition of Jamesonite and Warrenite. WALDEMAR T. SCHALLER (Zeitsch. Kryst. Min. 191 1 48 562-565).-The jamesonite formulct propobed by Spencer (Abstr. 1907 ii 700) is replaced by the simpler formula 4PbS,FeS,3Sb2S proposed by Loczka (Abstr. 1909 ii 153) the calculated percentages corresponding with these formulze being 7(l'b:,Fe:)S,4Sb,S3 ...............21-70 34'23 41.29 2-78 S. Sb. Pb. Fe. 4PbS,FeS,3Sb2S .................. 21 86 35-10 40'32 2 T 2 Warrenite (Eakins 1888) is shown to be a mixture of the brittle '' feather-ore " jamesonite and the flexible " feather-ore " plumosite (PbS,S b,S,). L. J. s. Optical Characters of the Q- and P-Modifications of Quartz and Leucite. FRITZ RINNE and R. KOLB (Jalwb. Afi~. 1910 ii 138-158).-The refractive indices are given for lines of several wave-lengths at various temperatures ranging from - 140' to + 765'. These were determined with prisms enclosed in a specially constructed electric oven or cooling chamber attached to the goniometer. The curves showing the results obtained with quartz exhibit an abrupt break at 570° corresponding with the change from a- t o @-quartz.The values for a-quartz a t 23' are W = 105442 E = 15533; for /3-quartz at 580° w = 1.5328 E = 1.5404 (line DJ. Leucite becomes optically isotropic at 714' and the plotted curves of the refracGive indices deviate in direction near this point but show no sudden break ; the change from Q- to p-leucite therefore takes place over a considerable interval of temperature. L. J. 8. Artificial Production of Nesquehoiiite. GIUSEPPE CESARO (Bull. Acad. Roy. Belg. 1910 844-845. Compare ?bid. 1910 749; Abstr. 1910 ii 49,613).-9 solution of sodium hydrogen carbonate and magnesium chloride was exposed outside to the low temperature at the end of November and the next day there were formed small transparent crystals of lansfordite (MgCO3,5H,O) together with crystalline globules composed of fine needles having the optical charactlers of nesqnehonite ( MgC0,,3H20).The simultaneous forma- tion of these two substances thus depends on the low temperature and not on pressure. Thaumasite from Beaver County Utah. 33. S. BUTLER and WALDEMAR T. SCHALLER (Amer. J. Sci. 1911 [iv] 31 131-134).- 'I'his mineral has hitherto been found only in Sweden and a t Yaterson in New Jersey. It has now been found as a filling in small fissures in metamorphosed dolomitic limestone in the Old Hickory copper and magnetite mine in the Rocky Range of Beaver Co. Utah. It is a pure white mineral with a fibrous structure and silky lustre and its lightness (sp. gr. 1.84) is a noticeable feature. Between crossed nicols the minute slender prisms give btraight extinction ; the L.J. S.ii. 210 ABSTRACTS OF CHEMICAL PAPERS. refractive indices are w > 1.500 E > 1,464. Analysis agrees w usual formula 3Ca0,Si02,S0,,C02 15H,O. SiO,. SO,. CO,. CaO. H,O. (Al,Fe),O,. MgO. Alkalis P,O,. 10'14 12-60 6-98 26'81 42.97 0.20 0-23 trace. th the Total. 99'93 L. J. S. Are Allophane Halloysite and Montmorillonite Simple Minerals or Mixtures of Colloidal Alumina and Silica? STANISLAUS J. THUGUTT (Centr. Min. 191 1 9$-103).-A review of the literature on this question is given (compare Stremme Abstr. 1908 ii 1041). The various clay minerals are capable of taking up organic colouring matters (methylene-blue rhodamine methyl-orange) but t h e varying nature of the colour reactions suggests that these minerals possess individuality and are not merely mixtures of colloidal hydrated alumina and silica.When moistened with cobalt nitrate solution and ignited some of these minerals do not give a blue colour Whilst others become blue only in part. This indicates that the alumina and silica must be chemically combined. The patchy distribution of the colours sometimes obtained indicates that the materials are not a1 ways homogeneous. L. J. S. Deposit of Alunite in the Liparite of Torniella in the Province of Grotweto. UGO PANICHI (Atti R. Accnd. Lincei 1910 Lv] 19 ii 666-664).-Analysis of a typical liparite of the district gave Loss on SiO,. Also,. Fe,O,. FeO. CaO. MgO. K,O. Na,O. heating Total. 72.29 14-40 1.69 0.31 1-34 0-48 4-18 2.67 2.39 99-75 A white deposit which occurs in abundance a t Marmaio and Pimale is not kaolin as has been hitherto believed but consists of alunite containing a little more silica and iron than the alunite of Tolfa. The mineral loses sulphur trioxide when heated and this loss of weight has been assumed to be due to water by previous investigators. Analysis of a sample of the mineral ga.ve SiO,. A1,0,. Fe,O,. SO,. H,O. K,O. Na,O. Total 1'99 39-04 0.53 33'26 13.74 9.77 2.94 100.27 The rock a t the base of the deposit a t Marrnaio is impregnated with the substance which when separated by levigat,ion gave similar analytical figures. It is noted that the rocks of the aeighbourhood of the deposit of alunite have suffered more change into kaolin than other similar rocks of the same district further removed from it. R. V. S.