Amphibolite, hornblendite, and related rocks
Gneiss, schist & quartzite. Paleoproterozoic, about 2,500 to 1,600 million years old. 1 crag on this site has its map point on it.
What the map says
Dark-colored rocks composed mainly of hornblende, quartz, plagioclase, biotite, and clinopyroxene in varying amounts. Commonly consists of interlayered hornblende gneiss, amphibolite, and other gneisses, including calc-silicate gneiss. Amounts of amphibolite and hornblende in unit not uniform but always sufficient to give an unusually dark appearance.
1:100,000 sheet: Trimble and others, 2003, U.S. Geological Survey Geologic Investigations Series I-856-H (1 crag). 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.