KERB pril, 1891.] Mineralogy and Petrography. 373 ish _bit. 04. dite lor Its in uc ys her kets the are de ite are an It. ha ds: nts in is te. al to ser The nt d -al als examined are P. †P. ‡P, ∞P, P¤, {Px, JP‡, 3P, ∞ P2, and x P3, making ninety-seven forms now known to occur in the species.Baumhauer" has discovered some small but good crystals of cryväte in a hand specimen from Evigtok, Greenland, so twinned that both individuals have their basal planes in common, and one appears to have been revolved about 88° 2' around an axis normal to the base. The limestone of Villefranque and of Biarritz, France, contains long needles of quartz and crystals of dipyr and albite, the first of which must have been formed contemporaneously with the limestone, while the last two were produced by the influence of an intrusive mass of diabase upon the enclosing rock.-Traube ascribes the differences in the values of the axial ratios of different sheelites to the amounts of molybdenum occurring in them. Analyses of many specimens reveal the fact that white and light yellow varities contain but little of this element, while the dark varieties contain quite large amounts, (1–8%). The axial ratio of the purest scheelite is 1 : 1.5315. that of calcium molybdenate is 1: 1.5458, and that of most scheelites between these limits.In the pegmatite veins cutting granite near Meissen, Saxony, Sauer and Ussing have found Baveno twins of microcline in which the gridiron structure is lacking. Lamellæ of albite are intergrown with the microcline, but sufficiently large areas of the latter mineral were found to allow of careful measurements of cleavage, angles, etc. The angle between the cleavage lines is 89° 30', and the refractive indices for sodium light,a=1.5224, 91.5264, 7=1.5295. The optical angle is 2V 83° 41'.-A pure white zine sulphide is mentioned by Mr. Robertson as occurring at Galena, Cherokee Co., Kansas. It is associated with sphalerite, and is in a form suggesting the moist, freshly prepared substance. It is saturated with water bearing a trace of sulphuric acid. Its composition is: Zn=63.70; S=30.77; Fe,0,= 2.40; Insol. = 2.52.—Rinne * gives some good illustrations of microcline structure in the feldspar of the Stockholm granite and of the Kyffhäuser gneiss, and suggests reasons for regarding it as a secondary phenomenon produced in nonstriated feldspar.—The phenacite reported by Mr. Yeates from " Ib., XVIII., 1890, p. 355 "Beaugey. Bull. Soc. Franc. d. Min., XIII., Feb., 1890, p. 59 Neues Jahrb. f. Min., etc., B. B. VII., p. 232. 24 Zeits. f. Kryst., XVIII., 1890, p. 192. 15 Amer. Jour. Sci., Aug., 1890, p. 161. Neues. Jahrb. f. Min., etc., 1890, II., p. 66. Amer. Jour. Sci., Sep., 1890, p. 259. Hebron, Me., turns out upon analysis to be apatite with a tabular habit. One New Minerals.-A new borate has been discovered imbedded in the form of small, colorless, transparent, or milky-white crystals in the pinnolite of Stassfurt, Germany. The crystals are monoclinic, with two perfect cleavages perpendicular to the plane of symmetry. of these is assumed as the base, and the other as the orthopinacoid, when the axial ratio becomes a : b: c = 2.1937: 1:1.73385; ß= 80° 12'. The forms observed are ∞ P∞, ∞P, -P, P, Poo, and -3P3. Hardness is 4-5; density, 2.127. The plane of the optical axes is perpendicular to the plane of symmetry, and makes with c an angle of °7 in acute P. A b. 2Hna 104° 27'. = The composition of the substance, as found by Baurath, is: The doe retr the fall га wate fract 2.75 twin which corresponds to H,Mg,K(BO2),+6H,O. The name Hintzeite has been given it by Milch.28 The same mineral is described under the name Heintzite by Leudecke.30 According to this investigator, the mineral is easily soluble in hydrochloric and nitric acids. analysis yielded results different from those above given, as follows: B,O= 60.53; MgO=12.23; K,O=7.39; H,O= 19.85. The axes chosen by Leudecke have the ratios a:b:c=1.2912: I: 1.7572 B: 57° 41' 4. The principal cleavages are thus parallel to oP and to P∞. The refractive index for sodium light vibrating parallel to A is 1.354. The other optical properties coincide with those determined by Milch. Prof. Groth suggests that neither of the two names suggested for the mineral be accepted until it is found which analysis is correct. -Powellite.-In a weathered fragment of bornite from the Devil's Mining Region, in Idaho, Mr. Melville 30 has discovered a mineral resembling scheelite in external appearance, but differing from it in composition. The crystals are small, prismatic, greenishyellow in color, with a hardness of 3.5, and a density of 4.526. They have a resinous lustre, and are semi-transparent and brittle. Measurements of angles indicate a tetragonal symmetry with a:c=1: 1.5445. The planes appearing oP, P, Poo, and P. The composition is: MOO, WO, SiO, CuO MgO Fe,O, Al,O, CuO S 58.58 10.28 3.25 25-55 28 Zeits. f. Kryst., XVIII., 1890, p. 479. 29 Ib., p. 481. 30 Amer. Jour. Sci., Feb., 1891, p. 141. .16 1.65 tr. tr. und. have mista Worm mark cordi are p hardr of its OP an musc and it const erous 31 Re Ba The mineral bears the same relation to calcium molybdate as scheelite does to the corresponding tungstate.An isotropic or weakly doubly refracting mineral occurs in the nepheline-syenite of a "massif” in the Kole Peninsula, Russia. Since its properties have not yet been fully determined, its discoverer, Ramsay, has not yet assigned to it a name. The mineral is red and transparent. It fuses easily, and yields water. It is attacked by acids with difficulty, has a low index of refraction, nña=1.5223, and possesses no cleavage. Its density is 2.753, and composition: SiO, Al,O,Fe ̧03 MnO CuO MgO Na0 K0 Loss 32 -Leverrierite occurs in small pseudohexagonal prisms that are twinned orthorhombic forms with a prismatic angle of 128°. They have a very perfect cleavage parallel to oP, so that they may easily be mistaken for mica. Often the prisms are twisted so that they resemble worm tubes to such perfection that they have been mistaken for organic markings, and have been described under the name bacillarites. According to Termier, all specimens of bacillarites examined by him are prisms of the new mineral, whose composition is H1ALSO The hardness of the substance is 1.5, and its density 2.3-2.4. The plane of its optical axes is ∞ Poo, with a negative acute bisectrix normal to op and an optical angle 2V 45°-52°. It may be distinguished from muscovite by its dark color, and from biotite by its weak pleochroism, and its weak double refraction. Leverrierite is found as a metamorphic constituent in carbonaceous clay slates, and in interstratified carboniferous eruptives. 31 Ref. Neues Jahrb. f. Min., etc., 1891, I., p. 98. 33 Bull. Soc. Franc. d. Min., XIII., 1890, p. 325. 10 From the AMERICAN NATURALIST, June, 1891. MINERALOGY AND PETROGRAPHY.' Petrographical News.-Mount Aviólo, in the southern Alps, consists in part of tonalite and in part of a quartz-mica-diorite, both of which intersect a series of crystalline schists, in which contact alteration has been effected. The tonalite is the rock so well known as comprising a large part of the Adamello group of the Alps. It is essentially a hornblendic quartz-mica-diorite. A garnetiferous variety is described by Salomon as an endomorphous contact product. It is characterized by the possession of plagioclase zonally developed, with the most acid zones on the exterior. The extinction of crystals varies as much as 30°, being by this much greater in the nucleus than in the peripheral portions. The quartz-mica-diorite forms a boss only two kilometers distant from that of the tonalite, but it is regarded by the author as having no genetical relation with the latter. These two masses of eruptives are surrounded by two series of schists: a younger series including phyllites and epidote-amphibolites, and an older one embracing gneiss and mica-schists. The former are in contact with the diorite, by which they have been changed into rocks composed essentially of quartz, muscovite, biotite, chlorite, and andalusite, of which the biotite and andalusite are new products. Corundum, tourmaline, sillimanite, and zircon are also new products, but are present only in small quantity. A cordierite-biotite rock, consisting of these minerals together with quartz, was found as an inclusion in the diorite. According to the degree of alteration effected in them the rocks are separated into two zones: an outer one, the zone of the ilmenite-frucht-schiefer, in which the phyllites have suffered merely the change of their chlorite into biotite, and an inner zone, in which andalusite is an important constituent. The schists around the tonalite belong to the older series of gneiss and mica-schists. These have been 1 Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. Zeits. d. deutsch. geol. Ges., XLII., 1890, p. 450. |