Mineralogy and Petrography. 1021 
SiO, Al,0, FeO CaO MgO H,O 
32.73 46.58 5.12 11.04 1.00 4.49 
The paper contains many points of interest, and is a final, incon- 
trovertible proof of the eruptive character of the massive rocks of 
the Cortlandt series.—In a paper in which the origin of quartz in 
basalts is discussed, Mr. Iddings! describes the microscopic appear- 
ance of quartz-bearing basalts from the Rio Grande cañon in New 
Mexico. Most of these are holocrystalline. They contain plagio- 
clase, augite, magnetite, olivine and rounded quartzes. The quartz 
is usually surrounded by shells composed of little augite crystals, 
which extend out into the body of the rock, and are sometimes 
partly included within the feldspar. It has the characteristics of 
the porphyritic crystals of more acid volcanic rocks, and is regarded 
as original, The main portion of the paper is taken up with the 
discussion of the conditions under which the production of por- 
phyritic quartz crystals might take place in a rock as basic as basalt. 
fter a thorough examination into the effects which temperature, 
pressure, and the presence of water vapor exert upon the crystalli- 
zation of a molten magma, Mr. Iddings concludes that the quartzes 
owe their origin to certain physical conditions attending an early 
period of the magma’s existence ; and that of these the most impor- 
tant is the presence of water vapor under } ressure. In the same 
aper the writer describes two new occurrences of quartz basalt. 
he first is a red compact rock from the vicinity of Santa Maria 
Basin, in Arizona. The second is a dark-colored, fine-grained rock 
from the S. E. base of Anita Peak, Colorado.—Kroustchoff? has 
recently described an inclusion in the basalt from Wingendorf, in 
Silesia, which differs from most basalt inclusions in that it contains 
anorthite. This mineral and enstatite make up the larger part of 
the inclusion, which contains in addition to these, augite, diallage, 
ae and various spinels. The enstatite was separated and ana- 
yzed :— 
SiO, Al,0, FeO MgO CaO Alkalies Loss 
56.96 49 8.11 33.65 4.32 tr. 26 
her grained streaks throughout the rock the augite has all been 
replaced by hornblende.—In an article on Mount upara, a crater 
in the Flagraian Fields, near Naples, Deecke* describes augite- 
* Amer, Jour. Sci., Sept., 1888, p. 208. 
; Min. u. Petrog. Mitth.. X., 1887, p. 329. 
, Klemm: Zeits. d. deutsch. geol. Gesell., x1., 1888, p. 184. 
Ib., xl., p. 166. 
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