Slab of banded Au-Ag ore with NAUMANNITE and QUARTZ (Var: Chalcedony) Knob Hill Mine (Golden Promise Mine), Klondike Mountain, Republic, Republic District, Ferry County, Washington, USA Naumannite (Ag2Se) and electrum (Au, Ag) are found within the ginguro bands (high-grade dark gray bands/uppermost dark band in photo). The lighter-colored layers are composed primarily of chalcedony and clay. Slabbed ore specimen is 16.5 x 10.2 x 2.6 cm (6-1/2 x 4 x 1 in) Ralph Noyes Collection Photo Copyright © 2014 Jeffrey M. Schwartz
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