At about 12% FeO, therefore, the optical character changes from positive to negative.

Rhodophosphite and Tetragophosphite.-The rare mineral locality at Horrsjöberg in Wermland, Sweden, is the source of these two new minerals recently described by Igelström. The rhodophosphite occurs in large quantities in layers reaching a thickness of 2! feet, so that it can be mined profitably. At one locality it is found in the form of hexagonal prisms. From the partial analysis, it appears to be chiefly a calcium phosphate, with considerable quantities of ferrous iron and manganese, also chlorine, fluorine, and sulphuric acid. The formula proposed is 20 (RO), P2O¿ + 4 (Ca Cl2, CaF ̧) + Ca SO, where R Ca, Mn, Fe, or Mg. The mineral is allied to svanbergite. Tetragophosphite occurs in "four-sided " plates, or as a coating on containing cyanite-damourite rock. The two an

the alyses are:

These lead to the formula (Fe, Mn, Mg, Ca), P2O + (A1,01), P,O,+3H,0. It is somewhat lighter blue than lazulite, which it seems here to replace. The "Gusblatt-phosphat" (light blue phos phate) from the Westana Mts., Prov. Skane, Sweden, analyzed by Blomstrand in 1868 seems to be undoubtedly the same mineral. assigned the formula (Ca, Mg), P,O, + (Al,O,), P,O,+ 3H2O.

8

6 Zeitschr. f. Kryst., XXV, pp. 433-436, 1895.

He

Miscellaneous Notes.-Von Zeynek' notes the occurrence of sulphur deposited in the canals carrying 1,000,000 gallons of water per day from the hot springs at Warasdin-Töplitz in Croatia.-Rohrers gives results of two very careful analyses of hematite from Elba. The average of the two is as follows: SiO, .49, Fe,0, 98.60, CaO .42, MgO .74, total 100.25.-In an article on the contact of minerals of the Adamello Group of mountains in South Tyrol, Salomon gives a detailed discussion of the Wernerite from Breno, with much of the literature relating to that mineral.-Duparc and Stroesco1 have recorded the results of their observations on the crystalline form and optical behavior of thymoquinone and eleven of its derivatives.-Gentil" describes the occurrence of large bundles of yellowish-white somewhat altered sillimanite needles in pegmatite from Algeria. Veins of albite and plates of muscovite are also mentioned. The same author makes a note of thomsonite, stilbite and analcite from an altered basic volcanic rock occurring near Dellys in the province of Algiers.-De Gramont13 is led by the observation of the electric spark between fragments of certain minerals which are good conductors of electricity, to a study of the spectra of the sparks thus produced. This method promises to be useful for the rapid determination of certain minerals, and for the detection of included substances which are present only in traces. The lines of the non-metallic, as well as of the metallic elements may be observed. De Gramont also describes the apparatus used by him, and gives the details concerning the spectra obtained from air from twenty-four of the elements, and from about a hundred minerals.-Termier" calls attention to the two forms of the dimorphous substance PbO. After discussing the optical and crystallographic properties of the orthorhombic modification, he shows that its crystals are grouped to imitate a higher symmetry. PbO is, therefore, a good example of a substance which not only shows pseudo-symmetry by the grouping of the separate crystals, but also appears in a second form in which the molecular grouping follows an allied higher symmetry.-Gonnard, in an article on French 7 Tscherm. Mitth., XV, p. 192, 1895.

8 Tscherm. Mitth., XV, pp. 184-187, 1895.

9 Tscherm. Mitth., XV, pp. 159-183, 1895.

10 Bull. Soc. Fr. Min., XVIII, pp. 126-141, 1895. 11 Bull. Soc. Fr. Min, XVIII, pp. 170-171, 1895. 12 L. c., p. 374.

13 Bull. Soc. Fr. Min., XVIII, pp. 173-373, 1895. 14 Bull. Soc. Fr. Min., XVIII, pp. 376-380, 1895. 15 Bull. Soc. Fr. Min., XVIII, pp. 382--390, 1895.

15

siderites, adds to the thirteen forms of that mineral previously known the three rhombohedra (0332), (3034), and (1012).-Termier and Richard conclude from their study of crystals of Ca,P,O, occurring in the slags of the iron works at Kladno, that they are pseudo orthorhombic, composed of monoclinic lamellæ. Measurements of the apparently orthorhombic form agree well enough with those of Miers to show that both had to deal with the same substance. The specific gravity is 2.93-3.1, mean index of refraction, about 1.64. For red light, 2 V 20° (?), and for blue light it is about 40°.-O. Nordenskiöld" finds edingtonite from Bôhlet, Sweden, to be orthorhombic hemihedral instead of tetragonal hemihedral, as previously supposed. Sp. G. 2.776, plane of optical axes = 010, negative bisectrix parallel to the vertical axis, 2 V for lithium light 52° 47', for sodium = 52° 55, and for thallium 53° 10′. The indices of refraction for the above kinds of light are also determined. The mean index for sodium light is 1.5492, and the double refraction is .016. In conclusion, the simi

larity of form with that of mesotype is shown by the axial ratios: Edingtonite ab: c.9872:1:.6733

Mesotype ab: 2c.9785: 1:.7072

-Goldschmidt's figures and describes a projection goniometer by means of which the position of crystal faces is projected directly upon paper, thus doing away with the reading of angles and with trigonometrical computation. The instrument seems to be in many ways convenient, but does not give the highest degree of accuracy. A contact goniometer of similar action is also briefly mentioned.

PETROGRAPHY.'

Geology of Point Sal, California.-The geology of Point Sal, the extreme northwestern corner of Santa Barbara County, California, has been carefully worked out by Fairbanks' with special reference to the igneous rocks found there. The sedimentary rocks constituting the point and the adjacent country are of miocene or later age. They

16 Bull. Soc. Fr. Min., XVIII, pp. 291--295, 1895.

17 Bull. Soc. Fr. Min., XVIII. pp. 395--398, 1895.

18 Zeitschr. f. Kryst., XXV, pp. 538--560, 1895.

1 Edited by Dr. W. S. Bayley, Colby University, Waterville, Me.

2 Bull. Dep. Geol. Univ. of Cal., Vol. 2, p. 1.

comprise volcanic ashes, gypsiferous clays and bituminous shales, the last named of which were regarded by Lawson as tuffs. The present author declares them to be organic deposits. The igneous rocks which penetrate these beds are all basic. They include gabbros, peridotites, basalts, diabases and rocks similar to those heretofore described as analcite diabases. These latter are all now considered by the author as representing the otherwise practically unknown type of the teschenites. The augitic variety of this rock has the general structure of the diabases, in which are large poikilitic plates of augite. Between the diabasic constituents are polyhedral grains of analcite, and, in what appear to have been cavities in the rock-mass, are little groups of crystals and crystalline masses of the same mineral. The pla gioclase in the rock is all zonal with nuclei of labrodorite surrounded by concentric zones of a more and more acid feldspar, the peripheral one being albite. An analysis of a coarse grained specimen gave:

SiO, AO, Fe̟O, FeO CaO MgO K2O Na2O P,O, Ign.

2

Total 49.61 19.18 2.12 5.01 10.05 4.94 1.04 5.62 .27 3.55-101.39 which corresponds very nearly to 43.3 per cent feldspar, with a density of 2.57, 32.3 per cent augite, 20 per cent analcite, 4 per cent magnetite and .04 per cent apatite. All of the analcite is supposed to be an alteration product of nepheline.

The basalts of the region include two types. One is the usual variety and the other an amygdaloidal and spheroidal variety that is intruded by diabases and diabasic gabbros. These last named rocks grade into one another. Both contain hornblende, some of which is regarded as secondary and some as primary. In addition to the diabasic-gabbros there are others associated with peridotites (and serpentines) in such a manner that both rocks are regarded as differentiated products of the same magma. The gabbro is sometimes massive. At other times it is possessed of a gneissic structure, often attended by a striping produced by the alternation of augitic and feldspathic bands. The structure is concluded, after study, to be the result of stretching.

Among the other basic rocks identified in the gabbro-peridotite complex are anorthosites, diorites, norites, lherzolites, picrites, saxonites, wehrlites, dunites and pyroxenites. Each type is well described and a discussion of the banding noticed in many of them is given in some detail.

Leucite-Basanites of Vulcanello.-After studying carefully the rocks on Vulcanello in the Lispari Islands, Bäckström3 concludes 3 Geol. För. i Stockh. Förhanl., XVIII, p. 155.

that the greater portion of them are leucite-basanites. They all contain phenocrysts of augite, labradorite, olivine and magnetite in a groundmass which is sometimes a holocrystalline aggregate of oligoclase, orthoclase, leucite and magnetite, and at other times of numerous leucites, small augites and iron oxides in a glassy matrix. The rocks are regarded as effusive types of lamprophyres (minettes or kersantites) a supposition which is the more probable from the fact that the effusives in the Lipari province are mainly feldspathic basalts, andesites, liparites and trachytes. Biotite and leucite are thought to be complementary minerals-the former separating from a siliceous magma under considerable pressure, and the latter from a magma of the same composition under surface pressure, under conditions favorable to the escape of the mineralizers fluorine and water. Leucite is not confined to

rocks rich in potash, nor is it necessarily characteristic of these. place may often be taken by biotite.

Its

A Squeezed Quartz-Porphyry.-A squeezed quartz-porphyry is described by Sederholm' as occurring at two places in the Parish of Karvia in Province Abo, Finland. In both it appears as dykes cutting granite. The rock consists mainly of microcline phenocrysts to which are often added growths of new microcline in optical continuity with the original crystals, phenocrysts of an acid plagioclase surrounded in many cases by microcline substance and quartz phenocrysts in a groundmass of orthoclase and quartz. The twinning of the microcline is more largely developed around quartz enclosures in the phenocrysts and near quartz veins than elsewhere in the crystals. The porphyritic quartzes occasionally retain their dehenhedral contours, but usually they are much deformed in outline and in their optical characteristics. Often the quartzes are so shattered that they now constitute lenticular areas of a quartz mosaic. The structure of the groundmass is in several types. In the most important one it consists of a micropegmatite of orthoclase and quartz containing shreds of chlorite, which in some cases are distributed so as to exhibit a fluidal arrangement. The granite through which the porphyry cuts is a coarse grained porphyritic variety composed of oligoclase, biotite and hornblende. On the contact with the dyke rocks it is crushed and much epidote is developed in it. Under the microscope it presents the usual aspects of a dynamically metamorphosed rock. In his discussion concerning the name to be applied to the porphyry, the author quotes from a letter by Dr. Williams in which the prefix 'apo' is defined as signifying that the rock Bull. Com. Geol. d'Finlande, No. 2, 1895.