Informally named for Blue River where it occurs in Johnston Co, OK in Midcontinent region. No type locality designated. Occurs in eastern Arbuckle Mountains in area of Wapanucka, Coleman, and Reagan in eastern Johnson and western Atoka Cos, OK. Gneiss is banded and foliated. Consists of intermediate oligoclase, quartz, and slightly perthitic microcline. Biotite, muscovite, iron oxides, sphene, apatite, and zircon are accessory minerals. Gneiss is fairly homogeneous and generally fine grained with sparse, erratically occurring phenocrysts of pink potash feldspar. Plagioclase averages about 45 percent, quartz 30 percent, and microcline 20 percent. Color index averages less than 4 percent. Intruded by or in fault contact with Tishomingo Granite. Also cut by amphibolite dikes. May be metamorphic equivalent of Precambrian Troy Granite and an unnamed granodiorite. Geologic map. Precambrian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Assigned a Precambrian age of 1396 +/-40 m.y. [Middle Proterozoic] based on U-Pb measurements on zircons. Samples taken from foliated, banded gneiss near large parking area at Blue Ridge Recreation Area, SW1/4 sec 5, T3S, R7E, Johnson Co, OK, on eastern side of eastern Arbuckle Mountains, in the Midcontinent region. Large error assigned to age is due to high common Pb concentrations and to uncertainty in correcting for it.

Source: GNU records (USGS DDS-6; Denver GNULEX).