1885. | Mineralogy and Petrography. 993 
Tyrol, and of the associated hornblende schists, which he regards 
as having undoubtedly been derived by its uralitization! Severa 
wood-cuts illustrate the different stages of the alteration as it was 
observed under the microscope, The writer finds that the schis- 
tose structure is developed in the rock in proportion as the alter- 
ation of the pyroxene to hornblende has progressed, and is hence 
inclined to attribute both to the action of great pressure. 
Two parallel series of alteration which have gone on in the 
gabbros of Wildschönau, the writer illustrates in the following 
manner : ; 
Normal-gabbro 
arm aes 
Beemer oE. 
Uralite-gabbro - Hornblende-gabbro 
(“ Gabbro-diorite” of Tornebohm 
and Williams) 
Actinolite or nephrite-schist Amphibolite 
m 
Serpentine Epidote-rock 
PETROGRAPHICAL News.—Barrois? and Des Cloizeaux® have re- 
cently made important contributions to our knowledge of the phy- 
sical characteristics of the minerals of the chloritoid group, which 
are becoming more and more generally recognized as widely dis- 
tributed rock constituents. Van Werveke* publishes the results 
of a new microscopical study of a large amount of petrographical 
material in which this class of minerals plays an important rôle. 
This consists of the ottrelite schists occurring near Ottré and Viel- 
Salm in the Ardennes. These he divides into ottrelite-phyllite 
proper, garnetiferous ottrelite-phyllite, magnetiferous ottrelite- 
phyllite and ottrelite-bearing quartz-breccia. Professor E. 
Cohen, formerly of Strassburg, who has recently been called to 
the University of Greifswald, has a Jetter in the Neues Jahrbuch 
fiir Mineralogie,’ in which he revises the determination of the 
diallage in the Schriesheim picrite, made by him some twelve 
years ago. The resemblance of this rock to certain olivine rocks 
occurring near Peekskill, on the Hudson river, is very striking. 
In them large bronze-like cleavage surfaces of hornblende are 
mottled with much smaller grains of olivine and pyroxene. An 
almost identical mineral occurs in the Schreisheim rock, which 
was formerly considered by Cohen as diallage, but which now, 
Ueber den Gabbro aus der Wildschönau in Tirol und die aus ihm hervorgehen-. 
oe Gesteine, Tschermak’s Min. und Petrog. Mitth., vil, 1885, pp: 
75 
* Bull. soc. min, de France, vit, p. 37, 1884. 
*Bull. soc. min, de France, vil, p. 80, 1884. 
* Neues Jahrbuch für Min, , etc., 1885, 1, pp. 227-235- 
j * 1885, 1, p. 
