1892.] Mineralogy and Petrography. 849 
‘pyroxene intermingled with calcite, with the pyroxene more or less 
altered into serpentine. A fragment of the rock free from calcite and 
serpentine gave: SiO, = 54.30; MgO = 18.33; FeO = 1.11; CaO 
== 25.00, a composition corresponding to Ca Mg (SiO,),. The blue 
color is supposed to be due to the ferrous iron present in the pyroxene. 
Two New Rocks.—Boninite is a bronzite limburgite from Peel 
Island, one of the Bonine group, near Japan. It is described by 
Petersen? and Kikuchi’ as consisting of phenocrysts of olivine, bron- 
zite and a few augites imbedded in a glass full of crystallites, some of 
which are sanidine. The rock is closely related to sanukite.® Mija- 
kite from Mijakeshima is an andesite with a reddish brown pyroxene, 
supposed to be triclinic, feldspar and glass, forming a groundmass in 
which are porphyritic crystals of bytownite, a little augite, hypers- 
. thene and biotite. The composition is: 
SiO, Al,O, Fe,O, FeO MnO MgO CaO Na,O K,O Loss Total. 
50.87 21.98 5.85 5.09 1.45 1.38 9.12 2.85 22 .43 = 99.24 
Optical Anomalies.—In a prize volume’ issued by the Fiirstlich 
Jablonowski Society of Leipzig, Brauns discusses critically and in 
great detail the various theories proposed in explanation of optical 
anomalies and gives a resumé of all the work done on individual 
minerals exhibiting the phenomena. About seventy substances in 
which anomalies have been discovered are treated in the second part 
of the volume, while in the first part the space is devoted to the his- 
torical and critical discussion of the theories. The anomalous bodies 
are divided into five groups according as the cause of their peculiari- 
ties is differently orientated lamelle; dimorphous enantiotropism of 
their substance, strain, isomorphous mixture or loss of water. In an 
appendix are grouped those minerals the cause of whose anomalies is 
unknown. Pyrenaite, the black garnet occurring in a black lime- 
stone at the Pic d’Eres Lids, Pyrenees, show such regular anomalies 
‘that Mallard” is enabled to determine the optical constants of the sub- 
*Jahrb. Hamburg. wissensch. Anst. viii, 1891, p. 1. 
"Tour. Coll. of Sci., Imp. Univ. Japan, iii, 1889, p. 67. Ref. Neues Jahrb. f. Min., 
etc., 1892, i, pp. 311 and 313. 
SAMER. NATURALIST, 1891, p. 368. 
°Die Optischen Anomalien der Krystalle. Leipzig, S. Hirzel, 1891. . Pl. 6, pp- 
10 and 370. 
Bull. Soc. Franç. d. Min., xiv, p. 293. 
