196 The American Geologist. September, 1894 
'/'//. process of Segregation as illustrated in tlu New Jersey Highlands. 
Ralph S. Tarr, [thaca, K. V. The various theories offered to account 
for the New Jersej iron ores were stated and objections pointed out. 
Tin- process of segregal ion was then discussed and the banding of some 
of the New Jersey gneisses and limestones described. An instance of 
segregation was given, where blue dolomitic limestone lias been altered 
id calcite with bands or imparities, sometimes crystallized, though orig- 
inally disseminated in minute grains through tlir dolomite. This pro- 
cess was studied in t he slide and the i-t-sultiiiir banding was in all respects, 
excepl in size, likethe coarse banding of the white limestone. The 
possible application of this to gneissic banding was then pointed out. 
Alunogen null Bauriti of New Mexico, with notes on tin geology of tlu l'p- 
per iri/,1 region. Wm. P. Blake, New Haven, Conn. The deposits of 
alunogen and bauxite are found in the upper Gila river region, about 
forty miles from Hanover. At Hanover the rock formations are Paleo- 
zoic metamorphic limestones and syenites of greater age, characterized 
by large deposits of iron and -zi nc ores. Further north the country is 
covered with a thick deposit of volcanic sediments and lavas, filling the 
ancient valleys. The alunogen occurs in these formations and exudes 
from the cliffs in places where there has apparently been solfataric ac- 
tion by which the rocks have been altered and left without much silica. 
This may have been removed by hot water and steam, but iron pyrites 
appears to have been an important factor in the changes and in the pro- 
duction of the alunogen, which is remarkably pure and free from iron. 
Bauxite is the result of the alteration of the volcanic rock in place and 
is. like the French bauxite, a residual product and not deposited from 
solutions. 
AstudyoftJu cherts of Missouri. P>\ Edmund Otis Hovey, New York 
city. The paper gave the results of work on some thirty-eighl speci- 
mens of chert from various localities in the Lower Mai/nesian and 
Lower Carboniferous strata of the state. The cherts from the former 
series are non-fossiliferous, while those from the latter are usually 
crowded with the remains of crinoids and other calcareous organisms. 
The cherts vary very much in color, texture and state of preservation. 
A petrographic discussion occupied a large part of the article. It was 
shown that the cherts were composed essentially of chalcedony, though 
quartz and opal are present in some specimens, the latter to a very lim- 
ited extent in this series. The chalcedony is usually in the form of a 
granular mosaic (in polarized light), but some of the material is aggre- 
gated into concentric spherules showing characteristic negative double 
refraction. Careful search for sponge spicules was made, but nothing 
whatever of the kind was found, with one extremely doubtful exception. 
Live regular siliceous oolites were noted from the Lower Magnesian. A 
table of eighteen chemical analyses accompanied the paper, in which it 
was brought out that in cherts not bearing calcareous fossils 
The si 2 is usually > 98.00? 
•• AloO.j + 1'Vo'o, is usuallv < l.on. 
'■ CaO-f Mg o isusuallj < .25? 
•' ILj < ) i ign) is usually < .;.">', 
Determinations on four of the samples showed onh comparatively 
small percentages of Si <)._, soluble in caustic potash. This fact, to- 
gether with the small amount of water present and the microscopic 
characters, shows thai verj little opal or amorphous silica occurs in 
these cherts. The author gave a brief resume of the theories which 
have been propounded to explain the origin of Bint, hornstone and chert, 
and gave it as his opinion that the Missouri cherts which he studied 
were due to chemical precipitation from the ocean at the time of the 
deposition of the strata in which thej occur. 
