Biotite-Quartz-Feldspar Gneiss (Middle Proterozoic)Biotite-Quartz-Feldspar Gneiss - Gray-weathering, locally rusty, gray to tan or greenish-gray, fine- to medium-coarse-grained, moderately layered and foliated gneiss that is variable in texture and composition. Composed of oligoclase, microcline microperthite, quartz, and biotite. Locally contains garnet, graphite, sillimanite, and opaque minerals.
Clinopyroxene-Quartz-Feldspar Gneiss (Middle Proterozoic)Clinopyroxene-Quartz-Feldspar Gneiss - Pinkish-gray- or pinkish-buff-weathering, white to pale-pinkish-white or light-gray, fine- to medium-grained, massive to moderately well-layered gneiss composed of microcline, quartz, oligoclase, clinopyroxene, and trace amounts of epidote, biotite, titanite, and opaque minerals. Commonly interlayered with amphibolite or pyroxene amphibolite.
Epidote Gneiss (Middle Proterozoic)Epidote Gneiss - Light-gray- to pinkish-white-weathering, light-grayish-pink to pinkish-white, medium-grained, moderately layered and foliated gneiss containing quartz, microcline, and epidote. Some phases contain scapolite. May be interlayered with and related to potassium-feldspar gneiss (Yk), and (or) clinopyroxene-quartz-feldspar gneiss (Ymp). Two elongate bodies mapped east of Franklin.
Hornblende Granite (Middle Proterozoic)Hornblende Granite - Pinkish-gray- to medium-buff-weathering, pinkish-white or light-pinkish-gray, medium- to coarse-grained, gneissoid to indistinctly foliated granite and sparse granite gneiss composed principally of microcline microperthite, quartz, oligoclase, and hornblende. Some phases are quartz syenite or quartz monzonite. Includes small bodies of pegmatite and amphibolite not shown on map. U-Pb age approximately 1,090 Ma (Drake and others, 1991b).
Hornblende-Quartz-Feldspar Gneiss (Middle Proterozoic)Hornblende-Quartz-Feldspar Gneiss - Pinkish-gray- to buff-weathering, light- pinkish-white to pinkish-gray, fine- to medium-grained, massive to moderately well layered gneiss containing microcline, quartz, oligoclase, hornblende, and magnetite. Locally contains garnet and biotite.
Microcline Gneiss (Middle Proterozoic)Microcline Gneiss - Light-gray- to pinkish-white-weathering, tan to pinkish-white, fine- to medium-grained, well-layered gneiss composed principally of quartz, microcline, and lesser amounts of oligoclase. Common accessory minerals include biotite, garnet, magnetite, and, locally, sillimanite.
Potassic Feldspar Gneiss (Middle Proterozoic)Potassic Feldspar Gneiss - Light-gray- to pinkish-buff-weathering, pinkish-white to light-pinkish-gray, fine- to medium-grained, moderately foliated gneiss and lesser amounts of granofels composed of quartz, microcline, microcline microperthite and local accessory amounts of biotite, garnet, sillimanite, and opaque minerals.
Pyroxene-Epidote Gneiss (Middle Proterozoic)Pyroxene-Epidote Gneiss - White- to light-gray-weathering, light-greenish-gray or greenish-buff, fine- to medium-grained, moderately layered and foliated gneiss composed principally of quartz, microcline, plagioclase, clinopyroxene, epidote, and sparse amounts of titanite. Some phases of this unit are quartz-rich. May be interlayered and probably related to pyroxene gneiss (Yp).
Pyroxene Gneiss (Middle Proterozoic)Pyroxene Gneiss - White- to tan-weathering, greenish-gray, fine- to medium-grained, well-layered gneiss containing oligoclase, clinopyroxene, variable amounts of quartz, and trace amounts of opaque minerals and titanite. Some phases contain scapolite and calcite. Commonly interlayered with pyroxene amphibolite or marble.