<p>Quartz vein in phyllite in the Precambrian of North Carolina, USA. (camera lens cap for scale)
</p><p>This is an outcrop of Anakeesta Formation in the Great Smoky Mountains.  It's one of many stratigraphic units in the ~50,000 feet thick Ocoee Supergroup.  The Ocoee has considerable deposits of sandstone and shale originally deposited as sands and muds in an ancient ocean trench.  Trenches form along subduction zones, where a tectonic plate composed of thin, heavy oceanic lithosphere dives down into the mantle below another tectonic plate of either oceanic lithosphere or thick, lightweight continental lithosphere.
</p><p>Rocks in the Anakeesta Formation were originally shales, but have been metamorphosed to phyllites.  Phyllite is a foliated, low to intermediate grade metamorphic rock dominated by mica.  It often has wrinkled and crinkled foliation surfaces.  The brownish coloration in this outcrop is iron oxide staining produced by oxidative weathering of pyrite in the phyllite.
</p><p>The light-colored, linear feature from top to bottom is a vein - a fracture that has since filled with one or more minerals (in this case, quartz).
</p><p>Stratigraphy: Anakeesta Formation, Great Smoky Group, Ocoee Supergroup, Neoproterozoic
</p>
Locality: outcrop at Newfound Gap (northwestern side of parking lot), southern side of Rt. 441 (Newfound Gap Road), Great Smoky Mountains National Park, next to the northern border of Swain County, far-western North Carolina (next to the Tennessee border), USA (35° 36’ 39.06" North latitude, 83° 25’ 34.02” West longitude)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/36842810336/">Quartz vein in phyllite (Anakeesta Formation, Neoproterozoic; Newfound Gap, Great Smoky Mountains, North Carolina, USA) 2</a>