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Montana Mine, Rochford District, Lawrence Co., South Dakota, USAi
Regional Level Types
Montana MineMine
Rochford DistrictMining District
Lawrence Co.County
South DakotaState
USACountry

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Key
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Latitude & Longitude (WGS84): 44° 9' 34'' North , 103° 44' 38'' West
Latitude & Longitude (decimal): 44.15944,-103.74389
GeoHash:G#: 9xy5pqbp2
Locality type:Mine
Köppen climate type:Dfb : Warm-summer humid continental climate
Nearest Settlements:
PlacePopulationDistance
Lead2,999 (2017)21.5km
Central City130 (2017)23.0km
Deadwood1,258 (2017)24.2km
Johnson Siding659 (2017)25.8km
Hill City995 (2017)28.6km


REF:Deposit:: U. S. BUREAU OF MINES, 1954, BLACK HILLS MINERAL ATLAS, SOUTH DAKOTA: PART I, BUREAU OF MINES INFORMATION CIRCULAR 7688 P1
Production:: U.S. BUREAU OF MINES, 1954, BLACK HILLS MINERAL ATLAS, SOUTH DAKOTA: PART I, BUREAU OF MINES INFORMATION CIRC
Commodities (Major) - Silver, Gold
Deposit Type: Replacement
Development Status: Past Producer
Host Rock Unit: Pahasapa Limestone
Structure: Strongly Folded Rocks With General Strike N 20 Deg W
Host Rock: Schist

Regions containing this locality

North America PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


4 valid minerals.

Rock Types Recorded

Note: this is a very new system on mindat.org and data is currently VERY limited. Please bear with us while we work towards adding this information!

Select Rock List Type

Alphabetical List Tree Diagram

Detailed Mineral List:

Cummingtonite
Formula: ☐{Mg2}{Mg5}(Si8O22)(OH)2
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Gold
Formula: Au
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Pyrite
Formula: FeS2
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Quartz
Formula: SiO2
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
Gold1.AA.05Au
Group 2 - Sulphides and Sulfosalts
Pyrite2.EB.05aFeS2
Group 4 - Oxides and Hydroxides
Quartz4.DA.05SiO2
Group 9 - Silicates
Cummingtonite9.DE.05☐{Mg2}{Mg5}(Si8O22)(OH)2

List of minerals arranged by Dana 8th Edition classification

Group 1 - NATIVE ELEMENTS AND ALLOYS
Metals, other than the Platinum Group
Gold1.1.1.1Au
Group 2 - SULFIDES
AmBnXp, with (m+n):p = 1:2
Pyrite2.12.1.1FeS2
Group 66 - INOSILICATES Double-Width,Unbranched Chains,(W=2)
Amphiboles - Mg-Fe-Mn-Li subgroup
Cummingtonite66.1.1.1☐{Mg2}{Mg5}(Si8O22)(OH)2
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2

List of minerals for each chemical element

HHydrogen
H Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
OOxygen
O Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
O QuartzSiO2
MgMagnesium
Mg Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
SiSilicon
Si Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
Si QuartzSiO2
SSulfur
S PyriteFeS2
FeIron
Fe PyriteFeS2
AuGold
Au GoldAu

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Paleoproterozoic
1600 - 2500 Ma



ID: 2472526
Metamorphosed younger alkalic basalt, tuff, and volcaniclastic rocks

Age: Proterozoic (1600 - 2500 Ma)

Description: Pillowed chloritic greenstone or amphibolite, and layered amphibole schist and amphibole-bearing or biotite-rich schist. Thin interflow deposits include various dark-gray and black schists, typically containing some sulfide minerals or carbon-rich strata, and lenses of massive metachert and banded siderite-metachert or cummingtonite-rich beds. In Lead area this unit is part of the Flag Rock Group (Hosted and Wright, 1923) and in Rochford area it is equivalent to the Rapid Creek Greenstone of the Flag Rock Group (Bayley, 1972b). In Mount Rushmore quadrangle, unit represents two apparent separate volcanic centers largely within unit Xqc. Correlated with the Crow Formation west of Custer (Redden, 1963), which has flows and agglomerate having generally similar trace-element abundances and is locally enriched in niobium and cesium, suggestive of alkalic volcanism. In Rochford area, unit intertongues with tuffaceous shale, tuff, and volcaniclastic rocks (unit Xtv) that have U-Pb zircon age of 1,884 ± 29 Ma (Redden and others, 1990). Maximum thickness about 1,000 m.

Reference: Redden, J.A., E. DeWitt. Maps Showing Geology, Structure, and Geophysics of the Central Black Hills, South Dakota. U.S. Geological Survey Scientific Investigations Map 2777. [73]

Paleoproterozoic
1600 - 2500 Ma



ID: 3191697
Paleoproterozoic crystalline metamorphic rocks

Age: Proterozoic (1600 - 2500 Ma)

Lithology: Paragneiss

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Paleoproterozoic
1600 - 2500 Ma



ID: 2974394
Metamorphosed Siltstone

Age: Proterozoic (1600 - 2500 Ma)

Description: Medium-gray to dark-greenish-gray phyllite, slate, and biotite schist containing minor chert and amphibolite. Locally intruded by thin metagabbro sills. Thickness 1,000-3,000 ft (305-914 m).

Comments: Original map source: Martin, J.E., Sawyer, J.F., Fahrenbach, M.D., Tomhave, D.W., and Schulz, L.D., 2004, Geologic Map of South Dakota: South Dakota Geological Survey, GM 10, scale 1:500,000.

Lithology: Major:{phyllite,slate,biotite schist}, Minor:{chert,amphibolite,metagabbro}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License


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