Naumannite with Gold (Electrum) from Knob Hill Mine, Golden Promise #2 Vein, Republic District, Ferry County, Washington

A short while ago, I was contacted by a retired mine geologist who had examples of the rare mineral naumannite that he wanted to sell. He began working for Day Mines in Leadville, Colorado in 1976 as a mine geologist.  In 1978 he was transferred to the Knob Hill Mine. Here is how he describes this specimen.

There is electrum within the bands of naumannite.  The black bands are primarily fine grained naumannite.  There are various shades within the quartz, each representing a different mineralizing fluid stage.

Texture - The texture displayed by this specimen is typical of low sulphidation epithermal systems.  Many of the world's richest ore bodies and the large silver ore bodies of Mexico exhibit these textures.  These from Republic exhibit several stages of mineralization and brecciation.  That is, the vein filled with quartz with or without gold and silver, then either there was movement on the fault breaking the quartz filling, or steam pressure broke the filling (much like one sees in Yellowstone, only more sporadic and more violent), and a new round of mineralization entered the vein.  One of the periods was very gold and silver rich, then that was later broken down and re-cemented. Ore geologists love this texture.

This specimen consists of a cut slab which has not been polished. Electrum is easily visible with the naked eye within the bands of naumannite.  No damage