Sunshine Mine

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The Sunshine Mine is located between the cities of Kellogg and Wallace in northern Idaho. It has been one of the world's largest and most profitable silver mines, having produced over 360 million ounces of silver since 2001.[1]

A 2007 Canadian report by Behre Dolbear & Company estimated measured and indicated resources of 31.51 million ounces of silver in 1.43 million tons at 21.8 ounces of silver per ton and inferred resources of 231.5 million ounces of silver in 2.28 million tons at 101.6 ounces of silver per ton. The Behre Dolbear report is considered historic in nature and illustrates the resource potential of the Sunshine Mine.

History[edit]

Sunshine Miners Memorial

The Sunshine Mine property had its beginning in 1884 when brothers True and Dennis Blake staked the Yankee Lode mining claim. The two brothers mined their claim for the next two decades. Following the death of the Blake brothers the mine went through a series of acquisitions; being owned and managed at various times by Dan Price and subsequently Sidney Shonts. Later, John Sawbridge, a mining entrepreneur from Yakima, Washington became interested in the mine. It is unclear when exactly Sawbridge became involved in the company, but he likely held stock in the company when the Sunshine Mining Company was officially formed in 1918. At this time the company's headquarters were in Spokane, Washington. The original officers of the company were Eugene C. Tousley, E. Ely and R. Ricaby. Tousley was a broker in the mining industry, working in Spokane. During this time W.F. Newton was the manager of the company [2] In approximately 1921 a group of businessmen and entrepreneurs from Yakima, Washington purchased a controlling interest in Sunshine Mining Company. John Sawbridge became and/or remained the President of the Company.[3] The Yakima businessmen who joined the Board at this time were Albert E. "A.E." Larson (a successful businessman and entrepreneur), Alexander Miller (a civic leader and businessman) and Nathan P. "N.P." Hull (a prominent Yakima orchardist and businessman). In 1929, following the death of N.P. Hull, the board named Hull's son Carroll M. Hull to the Board to fill the position vacated by his father (citation needed). Following the death of Sawbridge in 1931, Larson became President and served the company in that capacity until his own death in 1934.[4] At that time Robert M. Hardy (a Yakima native and President of the Yakima National Bank) became President.[5] He would remain President until his resignation in 1956, at which time his son succeeded him as President of the Company.[6] In 1921 a 25-ton per day mill was constructed. The mill was later expanded piecemeal and eventually reached a daily capacity of 500 tons. Soon after the concentrator was commissioned, the Sunshine tunnel was driven from the surface in an exploration effort which discovered higher quality ore historically identified as "Chinatown"

In 1935 the concentrator at the mine was upgraded with new ball mill grinding units and flotation cells increasing the capacity to 1,000 tons per day while attaining a recovery of 98%. The sinking of the new four-compartment vertical Jewell shaft was started, reaching the 2300 level in 1936.

In 1943 a crew drifting east on the 2700 level following the Silver Syndicate fault discovered the famous Chester vein.

It was primarily the exploitation of the Sunshine vein followed by the Chester vein that determined the present configuration of the underground workings. With the discovery of the Chester vein on the 2700 level and the ore body's distance from the Jewell shaft of approximately 4000 feet east - southeast, other internal shafts (the No. 4, No. 5 and No. 10 shafts, more properly defined as winzes) were sunk or raised to more efficiently service the operations. The other principal internal shaft is the No. 12 shaft, servicing the Copper vein and the West Syndicate vein in the western end of the mine.

In 1957, under the Presidency of Robert M. Hardy Jr. Sunshine Mining Company drilled the Medina No. 1 oil well, located immediately north of the town of Ocean City on the coast of Washington State.[7] This was a joint venture with J.W. Tanner, an Olympia, Washington businessman with specific interests in the oil industry.[8] Sunshine Mining Company purchased Tanner's interest in the company in 1958. Sunshine's Medina No. 1 well would produce 12,500 barrels of oil and remains Washington State's only commercially producing oil well. In 1961 the well was capped and production stopped.[9]

In 1960, sand-filling operations were introduced underground at Sunshine Mine. The mill tailings were classified so that the coarser material, approximately 45% of the total mill feed, was used for stope backfill.

In the morning of May 2, 1972, a fire broke out in the Sunshine Mine. According to the US Mine Rescue Association, 91 workers died from smoke inhalation or carbon monoxide poisoning; 83 men were rescued, 81 on May 2 and two on May 9. The mine was closed for seven months after the fire, which was one of the worst mining disasters in American history and is the worst disaster in Idaho's history. Today, a monument to the lost miners stands beside Interstate 90 near the mine.

By the end of 1988, the mine was at full production. Ore production was primarily from mining the Chester vein systems serviced by the No. 10 shaft and the remnants of the Sunshine and Rambo vein stopes referred to as the Footwall area on the 3700 and 3400 levels. The 4000 and 4200 level Copper vein was under development from the No. 12 shaft.

In 1989, the mine produced 4.8 million ounces of silver. Production from the high grade Copper vein stopes began to impact the silver production volumes. During 1990, the mine produced 5.4 million ounces of silver, the most since 1971. By now the high-grade Copper vein stopes on 4200 level were becoming substantial producers, while production from the 10 shaft stopes was dropping off.

In 1991 the silver price fell to $3.90 per ounce and the operation was losing money. A mining plan was put together to reduce losses substantially while waiting for prices to improve. This was referred to as the "small mine plan" and was implemented in June 1991. The operation headings underground were centralized by shutting down the outlying, more costly production and development headings, and limiting operation to day shift only. The mining operations were consolidated in the Copper vein area and the most productive headings in the "Footwall Area". The mine below the 5000 level was salvaged and allowed to fill with water. Production was cut in half, while the work force was reduced by 65%.

The West Chance vein was discovered in 1992. By late 1996 it was clear the ore body was of sufficient size and value to support the mine's return to full production. The reserves were then developed by trackless ramp and lateral development methods using LHD (Load-Haul-Dump) equipment. The working areas outside the West Chance were shut down and salvaged in an orderly fashion and all resources were directed toward the West Chance. By July 1997, the mine workings below the 4000 level were salvaged of all usable equipment and materials and allowed to begin filling with water. In 1995, Sunshine acquired the neighboring Consolidated Silver (ConSil) property consisting of the surface facilities and underground workings of the Silver Summit Mine. This mine has served as the Sunshine Mine's second access for years. The ConSil underground mine workings are primarily accessed by an adit to an internal 5600 feet shaft. The surface opening of this adit is located about two miles east of the Jewell shaft.

The mine ceased production in the first quarter of 2001 because of several factors. These included low silver prices and the lack of regular and consistent exploration and development due to prior management shifting cash flow from the mine to corporate expenses, debt and other projects.

At closure the mine reserves were 1.13 million tons containing 26.75 million ounces of silver at 23.6 ounces Ag/ton. Upon closing of the mine these 'Historic' or 'Legacy reserves' were reclassified to 'mineralized material' as required by United States Securities and Exchange Commission regulations. These "Legacy Resources" are now classified as Mineral Resources under the CIM Definition Standards.

From historical records beginning in 1904 the Sunshine Mine has produced 364,893,421 ounces of silver from 12,953,045 tons of ore through 2001 when the mine was closed. From January 1, 1998 to January 1, 2004 the average reserves carried by the mine were 1.38 million tons containing 32.20 million ounces of silver at 23.3 oz Ag/ton.

Current events[edit]

On November 2, 2009, Alberta Star Development Corp. announced that it has entered into a binding term sheet with Sterling Mining Company to acquire a controlling interest in Sterling and its assets and provide for financing of Sterling's ongoing operations. Alberta Star later gave up their pursuit of the mine in the face of competing interest.

On April 22, 2010, Sterling Mining Company announced that Court papers will be filed shortly seeking to approve a successful $24.0 million bid for the assets and stock of Sterling Mining Company, the operator of the historic Sunshine Mine. The successful bidder—with a cash price of $24.0 million—was Silver Opportunity Partners LLC (SOP). SOP is a privately held company owned by Thomas Kaplan. It is based in New York as part of the Electrum Group of Companies, an international investor in precious metal mines.

On February 14, 2012, the mine was evacuated after a sensor in a vent shaft detected elevated levels of carbon monoxide inside. Twelve people were underground at the time, during the evening. All were workers for an underground mining services contractor called The Redpath Group, with headquarters in North Bay, Ontario, Canada. The mine was evacuated and sealed. All intakes feeding oxygen into the mine had to be sealed off, and nitrogen was injected to further reduce oxygen levels and extinguish the fire. On June 12, 2012, working under the guidance of the federal Mine Safety and Health Administration (MSHA) the seal was broken on the shaft and crews reached the mine's 3,100-foot level where the fire started. Gas readings at the 3,100 level showed no carbon monoxide and appropriate levels of oxygen, indicating the fire was out.

Geology[edit]

The district is hosted by rocks of the Pre-Cambrian Belt super group, which is divided into the Prichard group, Ravalli group, Middle Carbonate group, and Missoula group. The Ravalli group contains the Revette and St. Regis formations that are the preferred host rocks for silver mineralization in the district. Ore deposits are localized within the 600 ft. thick St. Regis formation and the underlying upper members of the 3,000 ft thick Revette formation. The contact between the formations is indistinct and is locally picked as being the bottom of the lower-most distinct purple-colored interval in the St. Regis. Rock types include argillite, siltite, sericitic quartzite, and vitreous quartzite.

Infrastructure[edit]

The Sunshine Mine infrastructure is antiquated and will require repairs and renovations. Water and electric supplies are sufficient for near-term future use. Property access is by a 2 mile paved county road paralleling Big Creek that intersects US Interstate 90. Communications, including telephone are installed and operable.

Mineralization[edit]

Over 30 veins have been named and mined at the Sunshine Mine. While the initial work suggested distinct veins, some of these veins are actually offsets across post-ore structures and others represent parallel footwall or hanging wall veins. Principle vein systems in the mine include the Sunshine, Chester, Copper, Yankee girl and West Chance. The Sunshine and Chester veins have each produced over 100 million ounces of silver. Major veins strike east-west and dip about 65° to the south. Locally, dips range from 45° to 90°. Strike lengths exceed 2000 feet and dip lengths are two to three times greater than the strike length. Major veins are located between the faults at an angle of about 25° to the bounding faults. Veins vary in width from a few inches to over 30 feet, but are generally 1 to 5 feet thick. Ore minerals include tetrahedrite and galena with siderite and quartz as the principal gangue minerals. The silver content of the tetrahedrite varies and the silver to copper ratio in the ore ranges from 40:1 (opt Ag:%Cu) to over 100:1. Tetrahedrite occurs as blebs, fracture fillings, or in veinlets. Samples exceeding 200 oz/ton silver have been collected in the mine. Other minerals include pyrite and arsenopyrite with minor to trace amounts of chalcopyrite, sphalerite, boulangerite, bourmonite, pyrargyrite, and magnetite.

Notes and References[edit]

  • Brock, James (1995). The Sunshine Mine Disaster. University of Idaho Press. ISBN 0-89301-181-9. 
  • Olsen, Gregg (2005). The Deep Dark: Disaster and Redemption in America's Richest Silver Mine. New York: Crown Publishers. ISBN 0-609-61016-3. 
  • Behre Dolbear, NI43-101 report, New York, [1][vague]

External links[edit]

Coordinates: 47°30′55″N 116°03′57″W / 47.515349°N 116.065729°W / 47.515349; -116.065729