Silver-lead veins may or may not contain minor amounts of sphalerite. Silver-copper veins can also contain minor chalcopyrite, pyrite, and galena as well as trace amounts of other sulfosalts.

The Coeur Mine mineralization generally resembles that of the Galena Mine, in containing a complex vein set controlled largely by the pattern of faults, and the rheology of the Revett quartzitic and argillitic units. Mineralization at Coeur is entirely in tetrahedrite-dominated veins, with no galena-dominated veins.

The tetrahedrite of the Coeur Mine has a lower silver:copper ratio than that in the Galena Mine, about 20 ounces of silver per percent of copper.

Currently, most of the ore production is now coming from conventional cut and fill stopes.

The Coeur shaft is a three-compartment timbered shaft, 4,100 feet deep, which is used for exhaust ventilation and for hoisting of silver-lead ore from the Galena Mine and silver-copper ore from the Coeur Mine.

The majority of the mine production over the past few years has been silver-copper ores. This ore is treated in the Galena mill to produce a copper concentrate. Silver-lead ores are also produced, which are currently being treated in the Coeur mill.

Galena mill.
Silver-copper ore from the mine is hauled in 5-ton cars to a 400-ton coarse ore bin located adjacent to the mill. The ore is moved from the coarse bin by a Pioneer pan feeder to a chute that feeds into a 1-foot by 3-foot Kue Ken jaw crusher. Belts move the crushed ore to a 4- foot by 12-foot vibrating flat deck screen, where undersize particles are conveyed to a 300-ton fine ore bin.

The ore is then fed into a 9-foot by 12-foot ball mill, after passing a weightometer. Grab samples are taken from the conveyor to determine daily moisture content. The ball mill discharge passes over a 3-foot by 12-foot screen. Oversized particles are recirculated to the ball mill, while the undersize material is classified in Krebs cyclones. The ore then passes to a two-stage Denver feed sampler and into the rougher flotation circuit. The rougher circuit consists of four 100-cubic-foot Denver flotation cells.

Underflow is sent to the scavenger circuit consisting of four – 100 cubic foot Denver scavenger cells. The underflow from the scavenger circuit represents the final tails, while the overflow is sent to a 4-foot by 5-foot Allis Chalmers regrind mill before being returned to the middle of the rougher cells.

Concentrate is fed to a Galigher automatic sampler, and then pumped to a 10- foot high by 20 – foot diameter concentrate thickener tank. The thickened concentrates are pumped to an Eimco drum filter where scraper drops the final concentrates into 400-ton capacity bins. The scavenger final tailings are sent to a Heath & Sherwood automatic tailings sampler before being sent to the final tailings box.

The mill flow sheet for the Coeur mill is similar to the Galena mill.