AEGIRITE AND RIEBECKITE ROCKS FROM 
OKLAHOMA 
AUSTIN F. ROGERS 
Stanford University, California 
Several years ago the writer spent a short time in studying and 
collecting the igneous rocks of the Headquarters Mountains in Okla- 
homa. An examination of the rocks-some time afterward revealed 
the presence of aegirite and riebeckite, minerals which at the present 
time can scarcely be called rare, but are very interesting. Other 
occurrences of riebeckite in this country are: (1) granite of Quincy, 
Mass. ;7 (2) pegmatite of St. Peter’s Dome, Colorado;? (3) paisanite, 
Paisano Pass, ‘Texas. 
The Headquarters Mountain group comprises several low moun- 
tains at the extreme western border of the Wichita Range. The 
largest lies adjacent to and northwest of the town of Granite, Greer 
County, Oklahoma. There are several further to the northwest and 
a single one a little southeast of the town, all being west of the North 
Fork of the Red River.4 These mountains like the others of the 
Wichita Range to the east rise abruptly from the level plain which 
give them an archipelago character. 
THE COUNTRY ROCK 
The main mass of these mountains is made up of a coarse-graiaed 
red granite. It weathers to large, rounded bowlders. Fresh speci- 
mens are very difficult to obtain as the ferro-magnesian constituents 
are almost invariably altered. The average size of the constituent 
minerals is about 7™™. Under the microscope the rock is seen to be 
made up of orthoclase, albite, quartz, amphibole and zircon. The 
t Washington, Am. Jour. Sci., Vol. VI (1889), p. 180. 
2 Lacroix, C. R., Vol. CIX (1889). 
3 Osann, T. M. P. M., Vol. XV (1896), p. 437. 
4 For location see map, Plate II (opposite p. 54), ‘‘ Professional Paper No. 31.” 
U. S. Geol. Surv. On p. 58 of this paper a paragraph is given to description of this 
group of mountains. They are said to consist of red granite similar to that of the 
Wichita group. 
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