The MTM Project is a classic example of a Mississippi Valley Type ("MVT") Pb-Zn deposit.

Brecciation and zinc mineralization is associated with the Lower Ordovician upper Knox Group, which is the unit of interest on the MTM Project. The main members of upper Knox Group are the Mascot Dolomite and the Kingsport Formation. The Mascot Dolomite consists of predominantly very finely crystalline dolostone units of various shades of brown and gray interbedded with some limestone units or their dolomitized medium and coarsely crystalline equivalents. The very finely crystalline dolostones are considered to be primary in origin, that is, they formed very early in the history of the strata regardless of the exact dolomitization mechanism(s). The thickness of the Mascot ranges from 759 to 847 ft.

The upper Mascot includes the interval from the Knox unconformity to the M-3 marker. Thickness of this section is very variable primarily due to removal of upper units by pre-Chazyan erosion; in some areas of Central Tennessee most of the interval is missing. In Smith and Trousdale counties (the MTM Project area), the upper Mascot ranges from about 135 to 225 ft.

The upper part of the late breccia systems host the main economic zinc deposits. Sphalerite, fluorite, barite, marcasite, pyrite, calcite, dolomite, and quartz form varying proportions of the cement of the mineral-matrix breccia. Economic grade occurrences of sphalerite are not distributed uniformly th ........

Currently, three underground mines are in operation, Gordonsville, Cumberland and Elmwood.

Underground mining uses mechanized room-and-pillar and longhole mining methods. Ore is hauled to the shafts in underground trucks, hoisted to surface and conveyed to the ROM in the case of Gordonsville and truck hauled to the ROM in the case of Elmwood.

An open stope design and typical development layouts for drilling and extraction commences with production drilling either 76 mm upholes from the stope undercut or 102 mm downholes from a sub level depending on stope geometry and access constraints. Production holes are then loaded with ammonium nitrate fuel oil (ANFO) or ammonium nitrate emulsion (ANE) and blasted using modern electronic detonation and initiation systems. Stope blasting is conducted in a series of blast packets which
comprise a series of vertical rings grouped based on optimization of Zinc grade and available blasting void. The initial void is established by firing a blind slot raise followed by subsequent firing of production rings into the initial void. Blasted ore is remote mucked from the stope undercut to a designated remote stockpile where it is subsequently free-mucked to mine trucks and hauled to the nearest production shaft and hoisted to the surface to be transferred to the mill.

The depth of the mining areas appeared to be about 700 ft below surface (based on 7 deg decline, 5,500 ft long).

The primary mining f ........

Ore mined at the three facilities is processed into zinc concentrate in the mill at the Gordonsville site. The ore mined at Elmwood was originally milled and concentrated at the Elmwood site however the mill was de-commissioned and ore transported underground to the Gordonsville mill, while ore mined at Cumberland was transported overland by truck. The Gordonsville concentrator located in Smith County, Tennessee was commissioned in 1978. Employing conventional technology, the plant includes a crusher, heavy media separation circuit, a ball mill primary grinding circuit, cone crushing secondary and tertiary circuits, a series of rougher-scavenger flotation cells, and a concentrate filter system.

After crushing, the heavy media separation circuit at the mill uses ferrosilicon to float and differentiate the zinc ore from the rock delivered to the concentrator. Zinc concentrates produced at the filter are delivered, without any special drying, onto a covered slab outside the con ........