The Crescent Mine
Location
The Crescent Mine is located in Big Creek canyon approximately four miles south of the Interstate 90 just east of Kellogg, Idaho in the Coeur d' Alene mining district. Mining has been carried out in the District for more than 100 years; it is the only known mining area in North America to have produced over 1 billion ounces of silver. Ore bodies in the District are unique in that they are persistent at great depths far in excess of one mile. Geologists have not uncovered any evidence to date, which suggests a limit to the depth to which ore might extend.
Adjoining the Crescent Mine land position on the east side and less than 300 yards from the Hooper Tunnel (the main access for the lower Crescent) is the world famous Sunshine Mine. One of the richest silver mines in the world; the Sunshine has produced over 328 million ounces of silver, 71,000 tons of lead, 50,000 tons of copper and 37,500 tons of antimony. Bordering the Crescent Mine property on the west is the largest tonnage producer in the district, the Bunker Hill Mine with a total output of 3,119,121 tons of lead, 161,384,305 ounces of silver and 1,311,266 tons of zinc.
Ideally situated between these world-class ore bodies is the Crescent Mine, which has produced over 28 million ounces of silver, and may have the potential produce several times the amount of past production. Gross metal value of past production at today's silver prices (US$12 per ounce) exceeds US $300,000,000.
History
Development work began on the Upper Crescent mine at the turn of the century. By 1917, the mine had begun producing ore from along the Alhambra fault. During the period prior to 1922, the Big Creek Mining Co. Ltd owned the claims. In 1922, the mine workings from Big Creek 3 level to surface were under lease. Local people referred to the mine as the Anderson mine or the Big Creek mine.
In the 1920's the Big Creek Mining Company went into receiver-ship and the Bunker Hill and Sullivan Mining Company (The Bunker Hill Co.) purchased the property at County auction. First production under the new ownership began in 1927 from the property, since then it has been known as the Crescent Mine.
From 1917-1942, an estimated 300,000 tons of ore were produced from the surface to the 1,200 level. Averaging 20.0 oz. Ag/ton. The ore yielded six million ounces of silver, 1,375 tons of copper and 2,192 tons of lead.
In the summer of 1943, the Crescent Mine was closed. The Bunker Hill Company reopened the mine in 1951, and by June of 1954 the Ellis (No. 1) shaft had been sunk from the 1,200 level to the 3,100 level. By the end of March, 1963 the stopes developed between the 3,000 and 2,500 level had produced in excess of 3.5 million ounces of silver. The Bunker Hill and Crescent Mines were connected at the 3100 level by the Y-U Crosscut and ore from the Crescent was shipped underground to the Bunker and hoisted out the Bunker Hill No. 1 Shaft.
During 1976 and 1977 an intense geological research effort was launched to compile the Crescent Mine stratigraphic and structural controls.
Tabulated production from the Crescent Mine between 1924-1977, totaled 868.926 tons averaging 25.97 oz. Silver per ton, 0.19% Lead, 0.03% Zinc, and 0.40% Copper.
Extensive logging roads were constructed across the upper surface during 1980 and 1981. The Bunker Hill made a concentrated effort to map all rock exposures and copies of field geology sheets are available. The Bunker Hill Company shipped portions of the Big Creek 3 and Big Creek 4 dumps during 1980.
In December 1981, the Crescent and Bunker Hill Mines were closed. Bunker Limited Partnership announced the purchase of the Bunker Hill Company assets in November 1982. By 1983 normal Crescent Mine production had resumed for a short period. Bunker Limited Partnership declared bankruptcy in the early 1990's and ownership of the property was transferred to Shoshone County, Idaho and the U.S. Environmental Protection Agency.
Total proven, probable and projected ore prior to the Crescent Mine's final shutdown was 396,500 tons of ore with an average grade of 23.7 ounces per ton silver for a total resource of 9,395,380 ounces of silver.
Geology
The District in underlain by members of the Precambrian belt super-group rock formations, which in the area of the mine are, in descending order, the Wallace, St. Regis, and Revett Formations. This super-group extends east-westerly for many miles and hosts the numerous mines that have made the District one of the major lead-zinc producing areas in the world and the premier silver district in North America. Within the Coeur d' Alene Mining district, the largest silver producing mines have in the last 50 years been located to the east of the Bunker Hill. These include the Crescent, Sunshine, Silver Summit, Coeur, Galena, and Lucky Friday extending east-west about 12 miles. This string of properties is called the "Silver Belt".
Most ore occurrences in the Silver Belt are located in an area defined by generally east-west trending structures; the Polaris Fault on the north and the Big Creek fault along the south portion of the Silver Belt. A prominent major fold, the Big Creek anticline, has been traced throughout the length of the Silver Belt area. In the Crescent Mine the Big Creek anticline is a major structure composed on two known folds. The Alhambra and Syndicate faults occur in the folds and are associated with ore occurrences in the Crescent and Sunshine Mines.
A significant number of veins are present, including the East Footwall, Hook, South, Lead, Steep Lead, Gray Copper, Parker, North, Chalchopyrite, Paramount, Wolverine, and Butler veins. Most production has occurred from the East Footwall, Hook and South veins.
Potential
The Crescent Mine has excellent potential to host a high-grade world-class silver ore body. A number of significant factors create a remarkably bright out look for the Crescent. These include:
Location, the Crescent is literally located between two of America's most prominent mines the Sunshine and Bunker Hill, with combined silver production of over 400 million ounces.
Geology, the property is underlain by the most favorable conditions in the Coeur d' Alene district to yield ore discoveries. A combination of structures and favorable lithology at the contact of the St. Regis and Revett formations indicate potential for high-grade ore occurrences in portions of the mine that are still relatively unexplored and developed. The majority of ores in the Silver Belt occur in similar areas.
Near term mining potential, with the existence of significant mining, milling and processing infrastructure located nearby and known ore occurrences in the upper workings, profitable mining opportunities can be accomplished relatively quickly at the same time more reserves are being developed. Several veins and stopes still had good ore present prior to the cease of operations in the upper Crescent in 1940. The Alhambra vein was developed in the Taylor Stope for 60 ft. along strike, it ranges from one to a few feet in width and assays between 16 to 64 ounces per ton silver it is open both on strike and at depth. The Gray Copper vein was stoped at strike with the vein being between four and five feet of width and averaged 113 ounces per silver across a one-foot width. The vein is significantly un mined. Mine maps also show a five foot wide vein averaging 18 ounces across 5 feet in the Big Creek tunnel and an area 50 ft. long and 5 ft. wide averaging 112 ounces per ton. These are just a few examples of a number of targets for exploration and mining in the upper Crescent Mine.
High Grade ore bodies. The Crescent Mine was historically the highest-grade producer in the Silver Belt. While the average grade of Crescent historical production is between 25 and 30 ounces per ton, there were a number of years in which the average grade of production was greater and than 50 ounces per ton silver for the entire year.
Major areas of unexplored ground with the most favorable geology for high-grade discoveries. Historically the highest grade and most production in the Silver Belt come from the contact zone of the St. Regis and Revett Formations. Despite the fact that several veins in the Crescent are projected through this area it still remains relatively untouched. The area between the 1200 and 2500 level actually present the best potential geologically in the whole mine. Little exploration has been conducted in this area. It offers excellent potential for the discovery of numerous high-grade veins and ore shoots.
Past operations had limited production capabilities. As a result of Crescent Mine ore being hauled underground and then hoisted and processed through Bunker Hill Co. milling facilities, the property was never developed or mined on nearly the scale it could have supported. Facilities at the Bunker Hill Co. limited the amount of ore that could be processed so further development never occurred, subsequently, the Crescent is one of the few properties in the Silver Belt that remains highly prospective yet relatively un-mined compared to it's potential.
Favorable metal prices, with Silver over $12 per ounce market conditions are very favorable Coeur d' Alene district mines typically produce for around $5 per ounce silver. Lead and Zinc are at highs and the potential for high-grade lead ore bodies is good. Both the "Lead" vein and the "Steep Lead" vein are silver-lead bearing galena veins that were for the most part left un-mined as a result of low lead prices in previous era's.
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