1893.] Mineralogy and Petrography. 275 
rock because of the loss of its characteristic blue color through alter- 
ation. The list of minerals common to this rock and to those of the 
Laacher See is now complete, so that the belief in a common origin 
for them is rendered almost a certainty. 
C. W. Hall” gives a few notes on rocks collected from Central Wis- 
consin, describing very briefly hypersthene and quartz gabbros in 
which there is much secondary hornblende, and quartz diorites and 
gneisses regarded as squeezed gabbros. 
A fourchite boulder in which are large arfvedsonite phenocrysts is 
mentioned by Kemp” as occurring at Aurora, Cayuga Co., N. Y. The 
same author mentions the existence of rhyolite, hypersthene, andesite 
and andalusite-hornstone from near Gold Hill, Teole Co., Utah. 
Spherulites® of andalusite occur in the carboniferous clastic schists 
of Beaujeu, France. The schists are composed of black and white 
mica fragments in a paste of sericite and hematite. 
Turner” makes brief mention of basaltic, andesitic and rhyolitic 
lavas, whose source was the late Tertiary cone Mt. Ingalls, in Califor- 
nia. 
Crystallographic Study of Diopsides.—Some very careful 
crystallographic observations have been made by A. Schmidt" upon the 
diopsides of the Alathal, of Achmatowsk, of Nordmark, of the Ziller- 
thal and the Arany-Berg. Many crystals from each -of these famous 
localities were examined, and much new data was obtained concerning 
the mineral. The following new planes were discovered: 4P2 and 
5P§ on the white diopside from Achmatowsk; Pœ on the green 
variety from the same place; œ P6' in the Nordmark species; 2 P10, 
oo P4 and oo Pz on the nearly colorless small crystals from Schwarzen- 
stein in the Zillerthal, and œ P7 and P4 on the black Arany-Berg 
mineral. The form P4 appears in Goldschmidt’s ‘ Index,’ but no ref- 
erence to it could be found by the author in the original memoirs. 
The axial ratios of the different varieties are : 
Alathal 1.0895 : 1: 5894 8 = 74°15'47” 
Achmatowsk (white)......... ........ 1.0909 : 1 : 5899 6 = 74°10'42” 
Achmatowsk (green)...............00: 1.0951 : 1 : 5985 2 = 73°31'8” 
Minn. Ac. Nat. Science, III, No. 2, p. 251. 
“Trans. N. Y. Acad. Sci., xi, p. 92. 
Lévy. Bull. Soc. Franç d. Min., xv, 1892, p. 121. 
16Amer. Jour. Sci., Dec., 1892, p. 455. 
MZeits. f. Kryst., xxi, 1892, p. 1. 
