Big Branch Gneiss (TXpCAb;0)

State	Texas
Name	Big Branch Gneiss
Geologic age	preCambrian-Proterozoic
Original map label	pCb
Comments	intrudes Valley Springs Gneiss and Packsaddle Schist. Present in northeast Gillespe and northwest Blanco Counties. felsic gneiss,gneissic quartz-diorite,mafic gneiss,quartzmonzonite-augen gneiss,hornblende schist,graphite schist
Primary rock type	gneiss
Secondary rock type	schist
Other rock types
Lithologic constituents	Major Metamorphic > GneissGneissic quartz diorite, fine- to medium-grained, gray, heavily contaminated with partly digested remnants of Packsaddle Schist. Locally near Red Mountain, potassium metasomatism produced a quartz monzonite-augen gneiss rich in pink microcline phenocryst
Map references	Bureau of Economic Geology, 1992, Geologic Map of Texas: University of Texas at Austin, Virgil E. Barnes, project supervisor, Hartmann, B.M. and Scranton, D.F., cartography, scale 1:500,000
Unit references	Barnes, V.E., 1946, Texas Univ. Bureau of Economic Geology Pub. 4301, p. 56-57. Bureau of Economic Geology, 1981, Llano sheet, Geologic Atlas of Texas, Bureau of Economic Geology, University of Texas at Austin, scale 1:250,000.
Geographic coverage	Blanco - Gillespie - Llano