Summary:
The Revenue–Virginius Project’s vein deposits and the several associated veins within the mine are classified as volcanic-hosted epithermal base and precious metal vein type deposits.
At Virginius, chalcedonic quartz and cockscomb textures have been observed and late euhedral calcite is found in places. Fluid inclusion studies suggest that boiling did not occur in the system.
Mineralization in the District is found primarily in sub-vertical fissure veins and is classified as a telescoped epithermal quartz vein type deposit. The veins are characterized by somewhat constrained vertical extents generally less than 1,000 ft) and a vertical zoning that favors precious metals in the upper levels grading into more base-metal rich mineralization with depth.
The mineralogy includes galena, sphalerite, tetrahedrite, polybasite, chalcopyrite, pyrite, arsenopyrite, marcasite as well as ferroan rhodonite, calcian-ferroan rhodochrosite, quartz and chlorite.
Virginius Vein System
The most historically productive vein system at the Project is the Virginius and its northern extension, which is sometimes referred to as the Monongahela Vein. Reference to the Virginius Vein in this report will include the Monongahela. Between 1875 and 1906, this vein system is estimated to have produced over 15 Moz of silver with “significant lead and gold credits”.
The Virginius Vein in the north-northwest heading from the Revenue Tunnel is continuous over long strike (11,700 ft based on mapping) and dip distances and historic stoping occurs extensively within a zone 3,600 ft along strike and 2,500 vertical ft. The vein is typically averages about 1.5 ft or less in width although it can be as thick as 3 ft. The largest intercept on the vein recorded in the database was approximately 7 ft. It is reported to be a galena bearing vein, with perhaps 2 ft of altered and weakly mineralized rock on either side. Wallrock beyond that total width is weakly altered to unaltered and makes for relatively stable walls for mining purposes. More recent exposure by OSMI shows the vein widths can be more variable and reach widths of over 2 ft to 3 ft on a local scale in exposures during test stopes mined in 2016. The average width of the vein within the current Mineral Resources is estimated at approximately 1.3 ft.
The vein strikes from N45°W (near the 3rd Level portal) to N25°W in the northwest part of the mine (Coxe, 1985). In the upper workings, the vein is nearly vertical or even steeply northeast dipping in places. The vein is reported to outcrop at surface but is difficult to trace with confidence due to the rugged nature of the topography, snow cover and talus. An interpreted trace of the vein at surface has been used by SRK during the geological modelling stage. An inflection occurs at approximately the 6th level where the vein establishes a southwest dip that persists to the lowest workings, varying from 45° to 75° but typically dipping 65° to 75° southwest.
The vein tends to be narrow but continuous and typically consists of quartz with variable amounts of galena, tetrahedrite, polybasite. sphalerite, chalcopyrite and pyrite. The mineralogy of the vein is remarkably constant over the very large vertical and horizontal span, although the silver grade is variable (Benham, 1980). Tetrahedrite and polybasite are the principal silver minerals in the mine and can reach concentrations of 15% silver by weight.
Yellow Rose Vein
Development of the Revenue Tunnel provided deep access to several veins in the District including the Yellow Rose Vein. The Yellow Rose is a northwest trending vein sub-parallel to the Virginius located more than 5,000 ft to the northeast. The Yellow Rose was mined to a minor extent in the early years following development of the Revenue Tunnel and was explored by Ranchers, Sunshine and Star Mines over a length of approximately 3,800 ft and a down dip extension of approximately 550 ft. The vein zone has been mapped over 16,000 ft at surface. Like the Virginius, the Yellow Rose Vein dips steeply to the southwest and consists of several anastomosing veins within a broader structural zone. The mineralogy of the Yellow Rose is similar to the Virginius, but in general it is a wider vein averaging approximately 3 ft. The widest vein intercept sampled is approximately 10 ft with the smallest intercept at 0.1 ft. The Yellow Rose is considered to be a lower grade target than Virginius.
Terrible Vein System
The Terrible Vein has an overall N60°W strike with a steep southwesterly dip. Historical production came from workings with portals on three levels spaced at about 100 vertical feet with adits along the south slopes of Governor Blevation from 12,050 to 12,270 ft. A 4th and 5th Level were reached by means of internal shafts, but stoping only occurred above the 4th Level or above 11,950 ft elevation. The Terrible Vein system is intersected by the Revenue Tunnel and followed by a drift to the northwest of the tunnel for 1,202 ft and to the southeast for 850 ft. The vein tends to be narrow but continuous and typically consists of quartz with variable amounts of galena, tetrahedrite, polybasite, sphalerite, chalcopyrite and pyrite, similarly to the Virginius Vein and other veins in the vicinity.
Production
The primary products from the process plant include:
- A lead concentrate, into which 95% of the lead, 95% of the silver, 68% of the gold and 91% of the copper will be recovered;
- A zinc concentrate with minor amounts of silver and gold.
| Commodity | Product | Units | LOM (Projected) |
|
Silver
|
Payable metal
|
koz
| 13,099 |
|
Silver
|
Metal in concentrate
|
koz
| 13,860 |
|
Zinc
|
Concentrate
|
kt
| 15 |
|
Zinc
|
Payable metal
|
M lbs
| 15 |
|
Zinc
|
Metal in zinc concentrate
|
M lbs
| 23 |
|
Lead
|
Concentrate
|
kt
| 37 |
|
Lead
|
Payable metal
|
M lbs
| 51 |
|
Lead
|
Metal in lead concentrate
|
M lbs
| 54 |
|
Copper
|
Payable metal
|
k lbs
| 2,475 |
|
Copper
|
Metal in lead concentrate
|
k lbs
| 2,532 |
|
Gold
|
Payable metal
|
koz
| 21 |
|
Gold
|
Metal in concentrate
|
koz
| 23 |
|
Silver Equivalent
|
Payable metal
|
koz
| 17,680 |