Imágenes de páginas

hedral symmetry. The forms developed on some crystals from Monte Poni had suggested trapezohedral hemihedrism in the tetragonal system.

Wulfenite from several localities has been reported to be hemimorphic, on the strength of the polar development of the crystal form, but neither the etched figures nor the pyroelectric behavior of the crystals bears this out. Both wulfenite and scheelite act alike in these latter respects and appear to be pyramidal hemihedral, without difference in the two directions of the vertical axis.

Chalcolite, disthene, tourmaline, vesuvianite, dioptase, willemite, nepheline, beryl, adularia and some of the triclinic feldspars were also etched, with the result of confirming the higher symmetry in each case where doubt could exist. Nepheline, as already established by Baumbauer, belongs to the pyramidal hexagonal class of Groth (1st hemimorphic tetartohedral division of the hexagonal system, Liebisch).

Pollucite, Mangano-columbite and Microlite from Rumford, Maine.—These minerals were discovered in pegmatite associated with quartz, feldspar, muscovite, tourmaline, lepidolite, spodumene, amblygonite, beryl, cassiterite and columbite. They are described by H. W. Foote. The pollucite, though rare, occurs in rather large masses difficultly distinguishable from white quartz. The analysis proves the mineral to be chemically identical with that from Hebron, Maine, and seems to sustain the view of Wells that the formula is H,Cs, A1,(SiO2),.

The Mangano-tantalite is in the form of dark reddish brown crystals resembling rutile. A qualitative analysis revealed the presence of Mn, Ta and Ni. The specific gravity, 6.44, would indicate that the last two elements are present in about equal proportions. The form differs somewhat from columbite, as shown among other facts adduced, by the axial ratios. Columbite.

Mangano-columbite. a:b:c= .8285:1:.8898

.8359:1:.8817 Microlite in beautiful honey-yellow crystals 2 mm. in diameter have a specific gravity of 5.17. The prevailing form is the octahedron, , modified by the dodecahedron and sometimes by (113).

Epidote and its Optical Properties. The peculiar appearance of a gray epidote from Huntington, Mass., led to its detailed investigation by Forbes. The light color is evidently due to the low percentSiO,

3 Am. Jour. Sci., CLI, pp. 457-461, June, 1896. * Am. Jour. Sci., CLI, pp. 26--30, 1896.

age of iron, as shown by the subjoined mean of two closely agreeing analyses.

37.99 A1,02

29.53 FeO

5.67 Feo

.53 Mno

.21 Cao

23.85 HO



This corresponds with the accepted epidote formula. Some of the angles vary quite considerably from those given by Kokscharow—possibly due in one or two cases to the striated character of the faces.

The optical properties are unusual. The axis of greatest optical elasticity lies in the obtuse angle B, making an angle of 1° 51' to 2° 47' with the vertical axis, according to the nature of the light used. The optical sign is positive—an unusual thing for epidote. The indices are e=1.714, B = 1.716, and y=1.724. The double refraction is thus .010, the least value known for the mineral. The optical angle over a, 90° 32', is exceptionally large. A comparison of the data at hand seems to show that with increasing percentage of iron the double refraction becomes stronger, the index of refraction increases, while the optical angle (over a) grows larger, and when it passes 90° the crystals become optically negative.

Miscellaneous Notes.-Leiss gives details concerning several new models of optical instruments as manufactured by Fuess of Steglitz, near Berlin. The most important of these are a petrographical microscope, a theodolite-goniometer, an optical angle instrument, and a number of devices for universal motion.-Viola shows the application of the quaternion method to the discussion of crystal symmetry, and arrives at results concordant with those of Fedorow, Schön. flies and others.-Schwarzmann' describes a scale for reading directly with approximate accuracy the apparent optical angle 2E, without the labor of calculating it by Mallard's formula.-Crystallographers will be much interested in the results obtained by Rinne in certain experiments on heulandite. Anhydrous H,SO, abstracts 2 H,O from the molecule Ca Al, Si,O6 + 6 H,0 leaving Ca Al, SiO6 + 4H,0. The latter compound is optically quite different from the original heulandite, having, for example, a much higher double refraction and a dif. ferent plane of the optical axes. The change may be watched under a microscope, and takes place faster in some crystallographic directions than in others. Dilute sulphuric or hydrochloric acid gives a pseudomorph, which, after heating, is composed of almost pure Sio, (only 1.33 per cent bases). It has a specific gravity of 2.143, is optically biaxial with a small angle, and has weak double refraction. It is regarded as a new modification of SiO,, probably like Scacchi's “granulin.”

5 Neues Jahrb., B.B. X, pp. 179–195; also pp. 412-439, 1895. 6 Neues Jahrb., B.B. X, pp. 495-532, 1896. ? Neues Jahrb., 1896, Vol. I, pp. 52-56. 8 Neues Jahrb., 1896, Vol. I, pp. 139--148.

In continuation of his studies on Algerian minerals, Gentilo mentions with more or less detail calamine, smithsonite, sphalerite, calcite, galena, cerussite, limonite and barite from a number of zinc mines. Ilvaite and bustamite from Cape Boujaroun are also studied somewhat at length.-Dufeto publishes the results of a crystallographic study of four modifications of indophenol, also of several complicated organic and inorganic compounds which are not at all related to one another. -Lacroix" describes the microscopical characters of a number of compact or earthy minerals. They are not amorphous, as they appear to the naked eye, but are all micaceous and crystalline in ultimate structure.— Termier!? reports seven new forms, and a large number of rare ones, on a quartz crystal discovered on a block of gneiss in the lateral moraine of the lower Grindelwald glacier. The new forms are

The explanation of these rare faces is sought in the deposition of calcite on the quartz, followed by the formation of “temporary limiting" faces as the crystal again grows, and, finally, the solution of the out

. Bull. Soc. Fr. Min., XVIII, pp. 399-414, 1895. 10 Bull. Soc. Fr. Min., XVIII, pp. 414-426, 1895. 11 Bull. Soc. Fr. Min., XVIII, pp. 426-430, 1895. 19 Bull. Soc. Fr. Min., XVIII, pp. 443-457, 1895.

side of the quartz, thus exposing again the unusual faces. Some of the calcite layers are still present in the specimen.'

The new mineral lawsonite is more fully described by Ransome and Palache than was the case in the original paper by Ransome. The formula is H, Ca Al, Si,O10.— Walkerfinds that the sperrylite from the Sudbury district probably occurs originally included in chalcopyrite. The new face (10.5.2) was observed. The suggestion is made that Os and Ir occur replacing Pt in sperrylite, and an analysis of the products of the Murray mine, showing the presence of these elements, is given. (If, as this analysis would indicate, the two elements osmium and iridium are present in an amount equal to one quarter that of the platinum, it is difficult to suppose that they exist in the sperrylite, since Wells states specifically that he found no iridium in the sperrylite analyzed by him).-Adams and Harrington" describe a new alkali-hornblende chemically near an orthosilicate, and a titaniferous andradite from the nepheline-syenite from Dungannon, Hastings Co., Ontario.—Merrill notes an occurrence of free gold in a black mica granite from Sonora, Mexico, apparently as an original constituent of the rock.-Crocoite crystals from Mt. Dundas, on the west coast of Tasmania, measured and figured by Palache" present, in addition to the twelve known forms the new, though doubtful, prism (10.3.0).


Permian Land Vertebrata with Carapaces.- In the NatURALIST for 1895 (November) I described under the name of Dissorhophus a new genus of probably Ganocephalous Stegocephalia with an armadillo-like carapace. In the Proceedings of the American Philosoical Society for the same year and month I described a new family of Cotylosaurian Reptiles protected by a similar structure. These constitute the only forms of land vertebrates so constructed known from the paleozoic formations. The nearest approach to it previously known from the Permian is seen in the genus Zatrachys, where the 13 Zeitschr. f. Kryst., XXV, pp.


1895. 14 Zeitschr. f. Kryst., XXV, pp. 561-564, 1895. 15 Amer. Jour. Sci., CLI, pp. 210-218, 1896. 16 Am. Jour. Sci., CLI, pp. 309-311, 1896. 17 Am. Jour. Sci., CLI, pp. 389–390, 1896.

[ocr errors][merged small][graphic][ocr errors][subsumed][subsumed]

ns. са.


[subsumed][subsumed][ocr errors][subsumed]
[blocks in formation]
[blocks in formation]


« AnteriorContinuar »