MINERALOGICAL CHEMISTRY. Mineralogical Chemistry 33 Researches on Vulcanism. ALBERT BRUN (Arch. Xci. phys. mat. 1906 [iv] 22 425-448).-1t is suggested that the gases produced by the dissociation of ammonium chloride and ammonium nitrate which salts are of deep-seated origin are the main causes of volcanic explosions and that aqueous vapour is of little importance in this connexion. L. J. 8. Lead and Arsenic Minerals as Fumaroleproducts in the Recent Eruption of Veauvius. ALFRED LACROIX (Compt. rend. 1906 143 727-730).-During the recent oruption of Vesuvius numerous fumaroles were opened along fissures near the crater. On May 3 these were in an acid stage evolving water vapour charged with hydrochloric and sulphuric acids ; the temperature was 350O. Specimens of the solid material deposited by the fumaroles were collected on this date and alao subsequently in July and September The VOL.XCII. ii. 334 ABSTRACTS OF CHEMICAL PAPERS. most abundant consists like that of earlier eruptions of chlorides of iron potassium sodium calcium magnesium &c. but with the exception of erythrosiderite the mineral species are not well indi- vidualised. The chlorides are coated in places with realgar either as fused glassy isotropic crusts or as minute crystals. Galena was also noticed as small cubes (compare Abstr. 1906 ii 766) in association with crystals of magnetite (.or magnesioferrite) haematite pyrrhotite and pyrites. The galena would have been formed by the action of hydrogen sulphide on vapours of lead chloride. In some cases it has been altered t o lead chloride by the action of hydrochloric acid as shown by the existence of pseudomorphs of cotunnite after galena.Lead chloride is also present in the scoria and may be extracted by boiling water. This occurrence of lead is commented on in connexion with the formation of mineral-veins. L. J. S. Formation of Quartz in Silicate Fusions. P. D. QUENSEL (Cenntr. Min. 1906 657-664).-A mixture of oligoclase (74 parts) and silica (26 parts) was heated with 1-6'1 tungstic oxide for several houra at temperatures of 800- 1000' while superheated steam was forced through the mass. The microscopical examination of the glassy products proved the presence of minute crystals of quartz. The tungstic oxide acts as a '' mineraliser " by reducing the viscosity of the mass and lowering its temperature of fusion.Tridymite was formed when silica was fused with a large excess of sodium tungstate at 950-1000°. L. J. S. Dioxides of Elements of the Fourth Group of the Periodic System. JACOB BECKENKAMP (Zeit. Kryst. Min. 1906,42,448-474). -Constants are deduced for a theoretical tetragonal modification of silica and are compared with those of the known crystallised modifica- tions of silica; and the latter are compared with the pseudo-rhombo- hedral forms produced by the twinning of rutile. The relations between atomic weights and crystallographic constants in the several oxides are discussed. L. J. 8. [Cassiterite Jamesonite Tapiolite &c. from South Dakota.] WILLIAM P. HEADDEN (Proc. Colorado Sci. Soc. 1906 8 167-182).- Cccssiterite.-Analyses I-1V are of material from various mines in the Black Hills district of South Dakota; also anal.V of cassiterite from Mecklenberg North Carolina. Tantalite is associated with some of the specimens but appears to have no connexion with the presence or absence of tantalic acid in the cassiterite SnO,. Ta,O,. Pe,O,. SO,. Insol. Ign. Total. Sp. gr. I. 94-36 2.42 1-80 1.00 - - 99'58 6'622 11. 96'08 - 1.90 0.88 - 0.12 99-68 6.680 - - 100*11 6.767 111. 98.22 - 0 . i 2 - 0*64 0.34 99*92 IV. 98.13 - 0.43 - 1-40 - 99.96") 7.OI9 V. 95.18 3'82 '.I1 - \(FeO) * Also trace of CaO. Jccmesonite.-Columnar masses occur in qunrtz-veins at Sheridan,MINERALOGICAL CHEMISTRY. 85 Pennington Co. S.D. ; analysis V I agrees fairly closely with the formula 2 P bS ,S b,S,.Meneghinite. - Analysis VII of fibrous material from Rochford Pennington Co. S.D. agrees with 4PbS,Sb2S S. Sb. Pb. Fe. Cu. Zn. Co. Insol. Total. Sp. gr. VI. 18.90 26.99 51.15 1-30 0'24 0.05 trace 1.13 99-70 5.81 VII. 17.51 18.20 fi285 trace 0'86 - - 0'49 99'91 * 6'21 * Also traces of As Bi Cd. Hiibnerite.-Crystallised material from Cornstock mine Lawrence Go. S.D. gave anal. VIII; massive material from Sunday Gulch Pennington Co. S.D. anal. IX W03. SnO,. Cb,O,. Ta,O,. MnO. FeO. CaO. TotaI. VIII. 75'12 - - - 20.54 3-01 1.04 9 9 7 1 IX. 74.46 - - - 19.90 3.29 1.05 99.87" X. 0'11 0.07 4.29 78.61 - 16.85 - 100.24 t XI. 0 '59 3.90 78-58 - 15.60 - 99.96 $ - * Including Insol. 0.42 ; Ignition 0.75. t Including Cassiterite 0.31 ; TiO trace. $ Including Insol.1 '29. TapioZite.-Indistinct crystals from granite a t Cluster City S.D. were determined by Penfield to be tetragonal D. 7.218; analyses X and XI on the same sample of material. The method employed for the determination of tantalic and niobic acids is discussed. Analyses are also given of some zinc-blendes which phosphoresce when scratched ; the material is mixed with other minerals and the analyses suggest no cause for the phosphorescence. L. J. S. The Gas Observed when Tantalite is Attacked by Potass- ium Hydroxide. CAMILLE CHABRI~ and F. LEVALLOIS (Compt. rend. 1906 143 680-681).-When tantalite is heated t o redness in a vacuum there is a slight evolution of gas containing 84O/ carbon dioxide 1 2 * 4 O / nitrogen and 3*1"/ oxygen. If the mineral is subsequently fused in a vacuum in a Jena glass tube lined with silver with potassium hydroxide dried by prolonged fusion in a current of hydrogen water vapour is formed and a gas is evolved a t the rate of 11.5 to 14.5 C.C.per gram of tantalite which consists of 93*2O/ hydrogen 4.6'/ nitrogen and 1-2*/ oxygen. The nitrogen and oxygen are due t o air occluded in themineral the water and hydrogen are formed by the replacement of the ferrous oxide of the mineral by potassium oxide and its subsequent oxidation at the expense of the potassium hydroxide with the formatiou of hydrogen water and iron sesquioxide according to the equation 2TaO,,FeO + 4KOH = 4KTa0 + Fe203 + H,O + H (compare Moissan Abstr. 1881 74). Ilmenite (titaniferous iron) is similarly decomposed when fused with potassium hydroxide hydrogen and water being evolved ZTiO,,FeO + 4KOH = 2K2Ti0 + Fe,O + H,O + H,.M. A. W. 3-236 ABSTRACTS OF CHEMICAL PAPERS. Hellandite from Kragero Norway. WALDEMAR C. BROGGER (Zeit. Kryst. Min. 1906 42 417-439).-In the granitic pegmatite- veins which are quarried for felspar in the neighbourhood of Kragero the following minerals are found microcline-perthite quartz tourma- line orthite titanit e (yttrotitanite) thorite euxenite apatite pbenacite and hellandite ; brief descriptions are given of each of these and a detailed description of hellandite (Abstr. 1903 ii 657). Hellandite when fresh is nut-brown with a resinous lustre on the conchoidal fracture ; some of the optical characters are now given ; usually however the mineral is much altered and is then optically isotropic.The following are new analyses by L. Andersen-Aars both made on altered material; the more altered material of analysis I1 was white and earthy. I n analysis I 6°/0 of the water is lost gradually up to 500° and the remaining 5O/ is expelled only at a red heat. The latter appears therefore to enter into the con- stitution of the mineral and a new formula is given as Ca2R'3[ Err'( OH)J3[ SiO,],. SiO,. A1,0,. Fe,O,. Mn,O,. Ce,O,. Y203. Er,O,. Thop I. 23.66 10'12 2.56 5-91 1'01 19-29 15'43 0.62 11. 27'88 9.67 2-01 3-13 0.37 19'71 13-26 0.30 CaO. MgO. Na,O. K20. H,O. Total. I. 9-81 0.10 0.23 0.06 11-75 100.55 - 11. 9.97 0.13 0'41 13-09 99.93 A relation is traced between the crystallographic and chemical characters of hellandite guarinite danburite and topaz.Hellandite is near to but distinct from gadolinite kainosite rowlandite thalen- ite and yttrialite. L. J. S. Manganese-Garnet containing Yttrium. CARL BENEDICKS (Bull. Geol. Inst. Upsala 1906 7 27 1 -277).-Speseartite occurs at Klrarfvet near Falun in Sweden as rounded masse.' rarely as distinct crystals embedded in quartz and albite. Analyses Ly 0. Tenow of pale red material (I and 11) and of dark brown (111) gave SiO,. A1,0,. Y,O,. FeO. MnO. CaO. Total. Sp. gr. 11. 36'23 19.15 1'18 18.76 23.44 0.56 99.38) 4'197 I l l . 35'36 22.34 1'23 22-01 18-80 trace 99'74 4.068 IV. 5.5 n. d. 0.7 3 '1 1.4 11. d. I. 35.67 22 50 1-19 19'17 21.91 trace 100.44 - - Under 1V is given the compositiou of the portion which went into solution when the pale red material was digested with dilute hydro- chloric acid. The few previous analyses of garnets containing yttrium and those of Swedish spessartite are quoted. Alkali Quartz-Porphyries in Corsica. Remarkable Occur- rence of Orthoclase. J. DEPRAT (Compt. rend. 1906,143 753-756). -.Dykes of quartz-porphyry containing phenocrysts of quartz and anorthoclase and microliths of aegirite and riebeckite occur in con- nexion with the soda-granites of Corsica. A description is also given of simple and twinned crystals of orthoclase from a weathered mlcro- granulite frcim Corsica. L. J. S. L. J. S.