Crabtree Mine, Spruce Pine, Mitchell County, North Carolina, USA
Rather large vein in biotite schists about 1.5 to 2 m thick. Emerald is usually located near the contact of the pegmatite with schists. Towards the center of the vein, beryl becomes pale and changes to aquamarine and white or yellow beryl. Small emerald crystals, closely intergrown with feldspars, were mined as "emerald matrix".Ref: E.Ya. Kievlenko, Geology of gems, 2003, p. 79