514 The American Naturalist. i [June, 
MINERALOGY AND PETROGRAPY?’” 
Eleolite Rocks from Trans-Pecos Texas.—In a recent 
report on Trans-Pecos Texas Osann? gives a few brief notes on the 
igneous rocks of the region. The most interesting points in the arti- 
cle, which, on account of the short time allowed the author to prepare 
it, is little more than a collection of notes, refer to the alteration of 
limestones by granite and the production of a rock composed almost 
exclusively of calcium silicates ; to the existence of eleolite syenites and 
` phonolites in the Davis Mountains; to the occurrence of a tourmaline 
' schist in the Van Horn Mountains, and of altered diabases and 
squeezed porphyries in the Carriso Mountains. The eleolite syenite 
is a fine grained, light colored rock with the typical trachytic struc- 
ture. It contains orthoclase, eleolite and olivine as phenocrysts and 
' sodalite, aegyrite, malacolite, hornblende, arfvedsonite and the rare 
minerals ainigmatite, laavenite and pyrrhite in its groundmass. The 
olivine is nearly colorless in thin section. It usually plays the part 
of a nucleus around which the other dark components have crystal- 
lized. The pyroxene occurs in two generations. The amphiboles 
are also in two generations, and often these and the pyroxenes are 
intergrown with their ¢ axes and clinopinacoids coinciding. Ainig- 
matite is common in the rock, laavenite and pyrrhite are rare. The 
phonolites fall into two types. Those of the first type are charac- 
, terized by their fine grain, by the abundance of needles and grains of 
aegyrite in their groundmass, and the absence from them of amphibole 
and other accessory components. In the rocks of the second type are a few 
phenocrysts of feldspar and of nepheline, the latter of which are often 
bordered by adark corona of bisilicates. The most prominent of these 
are aegyrite and malacolite among the pyroxenes and among the 
amphiboles a variety with a strong pleochroism as follows: A=dark 
greenish blue; B=dark grayish brown; C=light yellowish brown. 
Cutting the eleolite syenite are dykes of tinguaite, monchiquite, 
alnoite, ouachitite, and a rock to which the author gives the name 
paisanite, since it was found in Paisano Pass in the Davis Mountains. 
This new rock consists of a few phenocrysts of quartz and of sanidine 
ina dense white matrix spotted with blue hornblende whose optical 
properties show it to be riebeckite. The white matrix is composed of 
‘Edited by Dr. W. S. Bayley, Colby University, Waterville. Me. 
Fourth Ann. Rep. Geol. Survey of Texas, p. 123. 
