MINERALOGICAL CHEMISTRY. 87 Mineralogical Chemistry. Formation of Coal. By S. STEIN (Chem. Centr., 1901, ii, 950; from Mugy. elhem. folySirat, 6, 39-42).-Wood mas heated with water in sealed tubes, as in the experiments of Cagniard de la Tour, and black masses resembling coal obtained ; these gave the following results on analysis : Temperature. 245" 250 255 265 2 75 280 290 Time. H per cent. 9 hours 5.4 6 9 2 5.1 6 9 9 5.2 5 Y , 4.7 6 ?, 4.5 5 9 9 4.1 5 9 ) 3% C per cent. 64-30 69.20 70.3 72.8 74.0 77.6 81.3 The increase in the amount of carbon depends on the pressure as well as on the temperature and duration of the experiment, since at atmospheric pressure for 2 days a t a red heat the amount of carbon never exceeded 78 per cent. L. J. 5. A Variety of Polydymite or Sychnodymite.By WILH. STAHL (%it. Kryst. Min., 1901,35, 289 ; from Be?-g-u. hiittenm. Zeit., 1899, 58, 182).-Light to dark grey, cubic crystals from the Siegthal gave on analysis : 23-46 5.70 26.80 3.86 39.28 0.47 99.57. cu. Ni. co. Fe. S. Insol. Total. This gives the same general formula (Co,Cu,Ni,Fe),S,, as both poly- dymite and sychnodymite, and approaches the latter i n the proportions in which the metals are present. Pyrites and Marcasite. L. J. S. By HENRY N. STOKES (Bull. U.S. Geol. Survey, 1901, No. 186 [Xer. A',, Chem. & Physics, No. 351, 1--SO).-- When pyrites arid mareasite are not distinctly crystallised it is often88 ABSTRACTS OF CHEMICAL PAPERS. difficult to distinguish between them, and the characters usually relied on for this purpose, namely, colour, sp.gr. and ease of oxidation, are not altogether trustworthy. It is pointed out that the true colour of marcasite is tin-white, the usual bronze-yellow being due to tarnish. The author has devised a chemical method for the dis- crimination of these minerals, and for their quantitative determination in mixtures. This method depends on the fact that when pyrites or marcasite is boiled with an excess of a solution of a ferric salt until the latter is completely reduced, the ratio of sulphur oxidised to mineral decomposed is perfectly definite and characteristic of each mineral, provided certain standard and easily controllable conditions are observed. With a boiling solution of iron ammonium alum con- taining 1 gram of ferric iron and 16 C.C. of 25 per cent.free sulph- uric acid per litre, the percentage of s u l p h r oxidised in pyrites is about 60.4, and in marcasite about 18 per cent, of the total sulphur. These figures are the characteristic oxidation coefficients, which depend, however, on the temperature and concentration of the solution. The oxidation of pyrites or marcasite to ferrous salt, sulphuric acid and free suIphur cannot be expressed by any single equation, but takes place according t o two or more, An empirical curve for the oxidation coefficients of mixtures of pyrites and marcasite in known proportions gives a means of quantitatively determining the com- position of naturally occurring mixtures of these minerals. The influence of various impurities on the results is described : the nature of the impurities can sometimes be distinguished by this method, for example, whether chalcopyrite or bornite is present in cupri- ferous pyrites, The determinations are made in an atmosphere of carbon dioxide, and a detailed description is given of the apparatus employed, Some of the experiments which have been made (Abstr., 1895,ii, 316 ; 1896, ii, 108; 1898, ii, 602 ; 1901, ii, 319) with the view of determining the state of combination or valency of iron in pyrites, &c., are here repeated, only to show that the evidence derived from such experiments is inconclusive.L. J. S. Hydrogothite, a Definite Hydrated Iron Oxide. By J. SAMOILOFF (Zed. Kryst. Min., 1901, 35, 272-274).-1n 1889, P. A. Zemjatschensky described as a new mineral, under the name hydro- gothite, a hydrated iron oxide with the formula 3Fe,0,,4H20; it mas found as thin veins in limonite in central Russia, and had a fibrous structure and cochineal-red colour.These observations, which have not been generally accepted, are confirmed by the present author, who considers hydrogothite to be a definite mineral species ; and he records its occurrence in the iron-ores of several localities in the Tula government. I t occurs as thin veins in, and as crusts 2-5 mm. thick on, massive limonite, and also as a later formation in the interior of hollow limonite concretions. Analysis gave : H20, 12.33-13.16 ; Fe203, 86-01 per cent,, agreeing with the above formula: phosphorus, aluminium and traces of manganese are also present. The observed sp. gr., 3.73, is probably too low.The powder of the mineral is tile-red in colour. Under the microscope are seen transparent plates H = 4.MINERALOGICAL CHEMISTRY. 89 or needles with a distinct cleavage in one direction, straight extinction, optically positive in the direction of the length, and very strong pleochroism. L. J. S. Ktypeite and Conchite. By HEINRICH VATER (Zeit. Kryst. Min., 1901, 35,149-17S).-Conchite (Abstr., 1901, ii., 168, 395) is identical with aragonite, and the same is probably also true of ktypeite (Abstr., 1898, ii, 604). L. J. S. Analyses of Magnesite [and Dolomite]. By JOZSEF LOCZEA (Zeit. Kryst. Min., 1901, 35, 282).--The following analyses are given of : I, grey magnesite, and 11, white dolomite, both from Jolsva, Gomor Go., Hungary: MgO. CaO. MnO. FeO.Fe,03. COP FeS,. Insol. Total. I. 44.63 - 0.i6 3.88 trace 51.34 0.19 0.04 100.24 11. 21-10 30.28 trace 0.98 trace 47.61 - 0.04 100*01 L. J. S. Pseudogaylussite. By CHARLES 0. TRECHMANN (Zeit. Kryst. Min., 1901, 35, 283-285. Compare Abstr., 1898, ii, 80).-A description, with photographic reproductions, is given of some crystals dredged up from the Clyde a t Cardross opposite Greenock. They are of a reddish- brown colour, with curved faces and rounded pyramidal terminations ; in cross-section they are square or rhomb-shaped. Sp. gr. 2575 and 2.602, but the material is slightly porous. Thin sections under the microscope show the material to consist mainly of minute (0,165 mm. diam.) spherules of calcite with radialIy fibrous structure. Analysis gave : Ca3(PO,),. CaCO,.MgCO,. Total. 5.52 83.52 9.03 98-07 Traces of silica, iron, manganese, chlorine, sulphuric anhydride and organic matter are also present. No new light is thrown on the origin of these peculiar pseudomorphs, which are also known by the names thinolite and jarrowite. L. J. S. Artificial Preparation of Monetite. By AUGUST DE SCHULTEN (Chem. Centi'., 1901, ii. 1128; from Bull. Xoc. franq. Min., 24, 323--326).-Crystals of anhydrous dicalcium phosphate or monetite have been prepared by slowly dropping a 0-6 per cent. solution of ammonia into a solution containing 70 grams of anhydrous calcium chloride, 226 grams of disodium hydrogen phosphate (Na,HPO,, 12H,O) in 500 C.C. of water and 80 C.C. of hydrochloric acid of sp. gr. 1.19. After remaining 2-3 weeks, dicalcium phosphate was found to have crystallised in transparent, triclinic plates [a : b : c = 1,049 : 1 : 1.0441 having a sp.gr. 2.928 at 15'. This preparation resembles, and may possibly be identical with, Kloos' mnrtinite, Ca,H,(PO,),,&H,O which has a sp. gr. 2.894. E. w. w. VOL. LXXXII. ii. 790 ABSTRACTS OF CHEMICAL PAPERS, Stilbiteand Foresite from the ElbaGranite. B~ERNESTOMANABSE (Jahrb. Min., 190l,ii, Ref. 28-31 ; AttiSoc.~oscanaXci.Nat.Mem., 1900, 17, 203-227).--Stilbi te occurs as a yellowish-white mass encrusting the tourmaline and other minerals in drusy cavities in the Elba granite. Analysis I is of radial aggregates of small crystals, and I1 of globular and sheaf shaped groups ; in both cases, details are given of the amounts of water expelled a t various temperatures.The first of these analyses agrees with the usual stilbite formula, which, according to Clarke's theory of the silicates (Abstr., 1897, ii, SO), is written as [A~(SIO,),A~H~]C~[A~(S~,O~)~C~H~A~],~H,O. This is referred to as typical stilbite. The second analysis with more silica requires one of the (SiO,) groups in this formula, to be replaced by the group (Si308), whilst in an earlier analysis by Grattarola and Sansoni with less silica, there are only two (Si,O,) groups : H,O. SiO,. Al,O,. CaO. Na,O. K,O. Total. I. 17.75 56.59 17.73 7.03 1-73 - 100*83 11. 1494 61.51 15.01 6.74 1.91 - 100.1 1 111. 16.66 48.93 27.56 5.16 1.14 trace 99.45 Foresite occurs like the stilbite, but is snow-white. It gave on analysis the results under 111, agreeing with those required for the formula 13H20, 1 2Si02,4A1203,2(Ca,Na2)0, which is written in con- formity with Clarke's striictural formula of stilbite by replacing H4 by four AI(OH), groups.I n discussing the origin of these zeolites, the following analyses are given of the Elba granite. I (also traces of MnO and Zr02) of the normal biotite-granite; I1 (also trace of MnO) of dark, fine-grained patches in the same ; 111, (also trace of B203) of white veins contain- ing the tourmaline druses : SiO,. A1,03.Fe0,. FeO. CaO. MgO. K,O. Na,O. P,O,. H,O. Total. I. 69.92 15 68 4'57 1.85 0.92 3.18 4-35 0.24 0-59 101.30 11. 70.21 15-72 5-03 2.11 1.07 3.25 3-66 0.29 0.48 101.82 111. 75.17 14.05 0.21 0.32 0.16 4.57 5.00 - 0.45 99.93 The orthoclase of this granite has the following composition ; 1, for the fresh material, 11, for the slightly altered, and 111, for the much altered material; whilst IV gives the composition of a zeolitic mixture representing a still further stage in the alteration of the felspar : SiO,.A1,0,. Fe,O,. CaO. KzO. Na,O. H,O. Total. I. 64-85 18.14 - 0.24 11.41 4.14 0.81 99.59 11. 51.64 23.98 0-18 3.82 15.37 100.00 111. 45.44 32-88 trace 2.08 [:%] 14.97 100*00 IT. 61.54 17.04 trace 4.92 1-75 2.03 13.70 100.98 The alteration of the orthoclase to zeolites has been effected by water charged with carbon dioxide. L. J. S. By H. STAD- LINGER (Zeit. Kryst. Min., 1901,35,313-315; from Sitx.-Bey.phys.-med. Xoc. Erkangen, 1899, 31, 1--63).-Large porphyritic crystals of fresh - Formation of Pseudophite in Granitic Rocks.MINERALOGICAL CHEMISTRY.91 microcline, with some intergrown plagioclase, from the granite of Strehlerberg in the Fichtelgebirge, gave on analysis the results under I ; sp. gr. 2.559. The following stages in its alteration are traced out, the end product being pseudomorphs of pseudophite, of which the composition is given under 11; sp. gr. 2.6397. The microcline first loses its lustre and becomes coated with rusty-brown limonite ; later, in the outer zone and along cleavage cracks, it becomes green; still later, the felspar is completely kaolinised, the colour passing to greyish- green, and finally to dark olive-green. Under the microscope, the following stages are recognised : complete kaolinisation of the enclosed laths of plagioclase ; commencing turbidity of the microcline ; forma- tion of secondary quartz and muscovite ; destruction of the cross- hatched ’ structure ; development in the exterior portions of a green colour and of scales of lithia-iron-mica ; accumulation of rutile needles ; appearance of zircon ; finally, the destruction of the grains of kaolin and the remains of the felspar.The analysis of the “pseudophite” shows it to be a chloritic sub- stance intermediate between pennine and clinochlore ; its composition can be expressed as 62.11 amesite molecules and 41.29 antigorite molecules. A granular dolomite a t the granite contact explains the large increase in the amount of magnesia : H20 Losson SO,. A1,03, Fe203. FeO. MnO. CaO. MgO. K20. Na,O. at 100O.ignition. Total. I. 62.96 19-36 0’40 1‘18 - 0’90 0.86 11.94 2.51 0.09 0.24 100.44 11.30’30 20.06 1.63 5’30 - 0.87 28.28 1.32 1-40 0.74 11.89 101.79 111. 45.80 6.52 18.03 6’13 1.52 4.63 1.76 1-17 1’39 9-90 3-95 100-80 Analysis I11 is of nontronite, which occurs near Strehlerberg as an alteration product of a schistose amphibolite : the material analysed contained some undecomposed hornblende, as well as a little mica, magnetite, and quartz. [Analyses of Garnet and Gold.] By W. REISS and A. STUBEL (Zeit Kryst. Min., 1901, 35, 298-301 ; from Geologische Studien in cler Republik Colombia. 11. Petrographie, Berlin, 1899).-The following mineral analyses are contained in an account of the minerals of Colombia. Rhombic dodecahedra of garnet of a greenish-grey colour, sometimes reddish in the interior, and optically anomalous, from La Topa, gave the following results.The magnesia probably belongs to enclosed malacolite. Loss on L. J. S. SiO,. A1,0,. Fe,O,. CaO. MgO. ignition. Total. 40.03 21.14 2.37 34.46 2.03 0.53 100.56 Alluvial gold from various localities gave, on analysis by Kollbeck, the following results; small amounts of copper and iron are also present : Au. 80’43 83’33 89.00 77-53 84’84 71.13 72.29 87-98 83.49 Ag. 17’89 13.56 9.43 20.89 13.63 24.09 24-42 11-03 14’79 L. J. 5. Theory of Tourmaline Mixtures. By GUSTAV TSCHERMAK (Zeit. Compare Abstr., 1900, ii, 217).-- The author upholds the Kryst. Min., 1901, 35, 209-219. A reply t o Penfield (Abstr., 1900, ii, 602). 7-292 ABSTRACTS OF CHEMJCAL PAPERS. view that the composition of tourmalines can be better expressed by the isomorphous mixing of two definite compounds rather than by tbe substitution formula of Penfield. 11. J. S. A Stony Meteorite which fell at Felix, Alabama. By GEORGE P. MERRILL (Proc. U.8. Nat. Museum, 1901, 24, 193--198).-This stone, weighing 2049 grams, was seen to fall on May 15th, 1900, near Felix in Perry County, Alabama. The broken surfaces are dark smoky grey, almost black in colour, The material is soft and friable and is very fine grained, with numerous small chondrules. Sp. gr. 3.78. The microscopic structure is described as follows : in a very dense, dark grey, seemingIy amorphous base are scattered olivine, augite and enstatite in the form of fragments and chondrules, and interspersed with occasional minute blebs of native iron and troilite. From analyses by P. Fireman of the metallic portion and of the soluble and insoluble silicates, the composition of the stone is : Fe. Ni. Co. Cu. SiO,. Al,O,. Cr,O,. FeO. FeS. 2.59 0.36 0.08 0.01 33.57 3.24 0.SO 26.22 4.76 MnO. Ni0,CoO. CaO. MgO, K,O Na,O. C. H,O. Total. 0.68 1.01 5.45 19.74 0.14 0.62 0.36 0.16 99.79 The mineralogical composition is : metal 3.04, troilite 4-76, chromite 1.17, graphite 0.36, soluble silicate (olivine in part) 72.60, insoluble silicate (enstatite and augite in part) 18.07 = 100*00. L, J. S.