Hornblende-plagioclase gneiss and amphibolite
Gneiss, schist & quartzite. Paleoproterozoic, about 2,500 to 1,600 million years old. 5 crags on this site have their map point on it.
What the map says
Dark-gray to black, weakly to strongly foliated, layered, mostly medium grained, hornblende-plagioclase gneiss and amphibolite containing variable amounts of biotite, quartz, and augite. Commonly has black-and-white mottled texture due to weathered plagioclase (white) and hornblende (black). Amphibolite contains greater than 50 percent amphibole. Hornblende-plagioclase gneiss contains interlayered amphibolite, particularly in Nederland 7.5-minute quadrangle, and minor calc-silicate gneiss (Xc) and cordierite-biotite gneiss (Xbc) (Gable, 1969). Commonly intimately interlayered with more felsic gneissic rocks, so many occurrences are included with other units
1:100,000 sheet: Kellogg and others, 2008, USGS Geologic Investigations Series 3000 (5 crags). A contact line at that scale is about 100 m wide on the ground.
Served by Macrostrat (CC BY 4.0). The wording is the map's own, quoted as a fact about the mapped unit, not about any one wall.