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United States

San Miguel Mine

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Overview

Mine TypeOpen Pit
StatusActive
Commodities
  • Lignite
Mining Method
  • Dragline
  • Truck & Shovel / Loader
Production Start... Lock
SnapshotThe San Miguel Mine delivers millions of tons of lignite coal to the adjacent San Miguel Electric Cooperative.

Owners

SourceSource
CompanyInterestOwnership
San Miguel Electric Cooperative, Inc. 100 % Direct
The San Miguel Lignite Mine is owned by San Miguel Electric Cooperative, Inc.

Contractors

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Deposit type

  • Sedimentary

Summary:

The mine extracts lignite coal from the Jackson formation, seams A, B, C and D ranging in thickness from 1.0 to 4.5 feet with a combined average total lignite thickness of approximately 9 feet. The seams are separated by relatively thin partings which vary in thickness from 0.5 to 1.5 feet.

The deposit consists of four or more thin (generally < 1 m or 3.3 ft thick) lignite benches that are separated by claystone and mudstone partings (fig. 2). The partings are composed of altered volcanic air-fall ash that has been reworked by tidal or channel processes associated with a back-barrier depositional environment (Snedden and Kersey, 1981; Gowan, 1985; Ayers, 1986; Senkayi and others, 1987; and Warwick and others, 1996).

In the mine area, the Jackson strata dip to the southeast about 17 m/km (90 ft/mi) (Ayers, 1986). Gowan (1985) and Ayers (1986) suggest that the mud-dominated sediments the comprise the floor, partings, and roof of the San Miguel lignite deposit originated in lagoonal mires landward (west) of the sandstone-dominated barrier island complex. The lignite-bearing interval is laterally persistent along strike for more than 40 kilometers (25 mi) (Ayers, 1986, 1989; Tewalt and others 1983).

The San Miguel lignite interval consists of four (or more) thin (generally <1 m or 3.3 ft thick) lignite benches that are separated by claystone and mudstone partings. The upper bed is designated as the A bed and is underlain by the B, C, and D beds (figs. 2, 3a) (Gowan, 1985). Tewalt and others (1983) referred to this interval as South Jackson seam no. 10. The rocks above the lignite beds are dominated by fine siltstone and claystone with occasional thin layers of gastropod and bivalve shells.

Kaiser (1982), Gowan (1985), and Ayers (1986, 1989) suggested that the rock partings within the San Miguel lignite deposit are composed of volcanic air-fall ash that has been reworked by possibly tidally influenced channel processes. Senkayi and others (1987) examined the partings in detail and found that most contained altered kaolinite and mixed detrital and volcanic quartz grains, thereby supporting the interpretation of a volcanic origin and subsequent detrital mixing of the sediment that forms these layers. These findings are consistent with the conclusions of Warwick and others (1996).

Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

Summary:

Production

CommodityUnits20222021202020192018201720162015
Lignite tons  ....  Subscribe  ....  Subscribe  ....  Subscribe3,003,7802,977,0993,070,7082,776,8582,574,464
All production numbers are expressed as ROM coal.

Operational metrics

Metrics202220212020201920182017
Coal tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe3,003,780 tons2,977,099 tons3,070,708 tons

Production Costs

Commodity production costs have not been reported.

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Jul 20, 2023
....................... Subscription required ....................... Subscription required Subscription required Jul 20, 2023
....................... Subscription required ....................... Subscription required Subscription required Jul 20, 2023
....................... Subscription required ....................... Subscription required Subscription required Jul 20, 2023

Total WorkforceYear
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Aerial view:

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