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Kensington Mica Mine (Gilmore Mine; B. H. Warner Mine), Wheaton, Montgomery Co., Maryland, USAi
Regional Level Types
Kensington Mica Mine (Gilmore Mine; B. H. Warner Mine)Mine
Wheaton- not defined -
Montgomery Co.County
MarylandState
USACountry

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Key
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Latitude & Longitude (WGS84):
39° 3' 24'' North , 77° 0' 47'' West
Latitude & Longitude (decimal):
Locality type:
Köppen climate type:
Nearest Settlements:
PlacePopulationDistance
Kemp Mill12,564 (2011)2.0km
Colesville14,647 (2011)2.3km
White Oak17,403 (2011)2.5km
Glenmont13,529 (2018)3.2km
Four Corners7,945 (2011)4.0km


Known as the Kensington or Gilmore Mica Mine
Located in Wheaton, Maryland (a suburb of Washington, DC)
Years of operation - 1882 to approx. 1914
This was a mica mine in pegmatite.

Remains of the Kensington Mica Mine can be found in what is now the "Springbrook Forest" subdivision (Wheaton, Maryland) and the adjoining "Northwest Branch Park." Little remains of the workings, which consisted of two shafts, a number of dumps, and a large cut through the pegmatite. The trenches used to float the mica in the seperating process are still extant and a very small portion of the dump piles remain, extending down into the park on the west side of Northwest Branch. An old shack, associated with the mine, still exists in the park as well. Some of the driveway borders for homes along Stonington and Remington Drive are decorated with pegmatite material left from the mining operation, some encrusted with large almandine garnets and splays of schorl.

After heavy rain, small books of mica can be seen washed out onto some of the streets of the neighborhood, especially at the corner of Remington Drive and Stonington Drive.

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


11 valid minerals. 1 erroneous literature entry.

Detailed Mineral List:

Albite
Formula: Na(AlSi3O8)
Reference: Ref.: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
'Almandine-Spessartine Series'
Reference: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
Autunite
Formula: Ca(UO2)2(PO4)2 · 11H2O
Reference: Rocks & Min.: 11: 8-9.; American Mineralogist (1926) 11:35-38
Bertrandite
Formula: Be4(Si2O7)(OH)2
Reference: Ref.: Minerals in the Washington D.C. Area.
Beryl
Formula: Be3Al2(Si6O18)
Reference: Rocks & Min.: 11: 8-9.; American Mineralogist (1926) 11:35-38
Beryl var: Heliodor
Formula: Be3Al2(Si6O18)
Reference: MacFall, 1951. Gem Hunter's Guide, 1st ed.
Fluorapatite
Formula: Ca5(PO4)3F
Reference: Rocks & Min.: 11: 8-9.; American Mineralogist (1926) 11:35-38
Gahnite
Formula: ZnAl2O4
Reference: Ref.: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
'Limonite'
Formula: (Fe,O,OH,H2O)
Reference: Ref.: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
Microcline
Formula: K(AlSi3O8)
Reference: Ref.: Minerals in the Washington D.C. Area.
'Microlite Group' ?
Formula: A2-mTa2X6-wZ-n
Reference: Ref.: Minerals in the Washington D.C. Area.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Reference: Rocks & Min.: 11: 8-9.; American Mineralogist (1926) 11:35-38
Orthoclase
Formula: K(AlSi3O8)
Description: Microcline - obsolete identification
Reference: Rocks & Min.: 11: 8-9.
'Pyrochlore Group' ?
Formula: A2Nb2(O,OH)6Z
Reference: Ref.: Minerals in the Washington D.C. Area.
Quartz
Formula: SiO2
Reference: Rocks & Min.: 11: 8-9.; American Mineralogist (1926) 11:35-38
Schorl
Formula: Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: Ref.: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
Spessartine ?
Formula: Mn2+3Al2(SiO4)3
Description: Spessartine is unlikely as this is a simple, undifferentiated pegmatite.
Reference: Ref.: Minerals in the Washington D.C. Area.; American Mineralogist (1926) 11:35-38
'Wad'
Reference: American Mineralogist (1926) 11:35-38
'Zinnwaldite' ?
Reference: Ref.: Minerals in the Washington D.C. Area.

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Gahnite4.BB.05ZnAl2O4
'Microlite Group' ?4.00.A2-mTa2X6-wZ-n
'Pyrochlore Group' ?4.00.A2Nb2(O,OH)6Z
Quartz4.DA.05SiO2
Group 8 - Phosphates, Arsenates and Vanadates
Autunite8.EB.05Ca(UO2)2(PO4)2 · 11H2O
Fluorapatite8.BN.05Ca5(PO4)3F
Group 9 - Silicates
Albite9.FA.35Na(AlSi3O8)
Bertrandite9.BD.05Be4(Si2O7)(OH)2
Beryl9.CJ.05Be3Al2(Si6O18)
var: Heliodor9.CJ.05Be3Al2(Si6O18)
Microcline9.FA.30K(AlSi3O8)
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
Orthoclase ?9.FA.30K(AlSi3O8)
Schorl9.CK.05Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Spessartine ?9.AD.25Mn2+3Al2(SiO4)3
Unclassified Minerals, Rocks, etc.
'Almandine-Spessartine Series'-
'Limonite'-(Fe,O,OH,H2O)
'Wad'-
'Zinnwaldite' ?-

List of minerals arranged by Dana 8th Edition classification

Group 7 - MULTIPLE OXIDES
AB2X4
Gahnite7.2.1.4ZnAl2O4
Group 8 - MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM
A2B2O6(O,OH,F)
'Microlite Group' ?8.2.2.1A2-mTa2X6-wZ-n
'Pyrochlore Group' ?8.2.1.1A2Nb2(O,OH)6Z
Group 40 - HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
AB2(XO4)2·xH2O, containing (UO2)2+
Autunite40.2a.1.1Ca(UO2)2(PO4)2 · 11H2O
Group 41 - ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
A5(XO4)3Zq
Fluorapatite41.8.1.1Ca5(PO4)3F
Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in [6] and >[6] coordination
Spessartine ?51.4.3a.3Mn2+3Al2(SiO4)3
Group 56 - SOROSILICATES Si2O7 Groups, With Additional O, OH, F and H2O
Si2O7 Groups and O, OH, F, and H2O with cations in [4] coordination
Bertrandite56.1.1.1Be4(Si2O7)(OH)2
Group 61 - CYCLOSILICATES Six-Membered Rings
Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution
Beryl61.1.1.1Be3Al2(Si6O18)
Six-Membered Rings with borate groups
Schorl61.3.1.10Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Muscovite71.2.2a.1KAl2(AlSi3O10)(OH)2
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Group 76 - TECTOSILICATES Al-Si Framework
Al-Si Framework with Al-Si frameworks
Albite76.1.3.1Na(AlSi3O8)
Microcline76.1.1.5K(AlSi3O8)
Orthoclase ?76.1.1.1K(AlSi3O8)
Unclassified Minerals, Mixtures, etc.
'Almandine-Spessartine Series'-
Beryl
var: Heliodor
-Be3Al2(Si6O18)
'Limonite'-(Fe,O,OH,H2O)
'Wad'-
'Zinnwaldite' ?-

List of minerals for each chemical element

HHydrogen
H AutuniteCa(UO2)2(PO4)2 · 11H2O
H MuscoviteKAl2(AlSi3O10)(OH)2
H BertranditeBe4(Si2O7)(OH)2
H Limonite(Fe,O,OH,H2O)
H SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
H Pyrochlore GroupA2Nb2(O,OH)6Z
BeBeryllium
Be BerylBe3Al2(Si6O18)
Be Beryl (var: Heliodor)Be3Al2(Si6O18)
Be BertranditeBe4(Si2O7)(OH)2
BBoron
B SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
OOxygen
O BerylBe3Al2(Si6O18)
O FluorapatiteCa5(PO4)3F
O AutuniteCa(UO2)2(PO4)2 · 11H2O
O MuscoviteKAl2(AlSi3O10)(OH)2
O QuartzSiO2
O Beryl (var: Heliodor)Be3Al2(Si6O18)
O AlbiteNa(AlSi3O8)
O BertranditeBe4(Si2O7)(OH)2
O GahniteZnAl2O4
O Limonite(Fe,O,OH,H2O)
O MicroclineK(AlSi3O8)
O SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
O Pyrochlore GroupA2Nb2(O,OH)6Z
O SpessartineMn32+Al2(SiO4)3
O OrthoclaseK(AlSi3O8)
FFluorine
F FluorapatiteCa5(PO4)3F
NaSodium
Na AlbiteNa(AlSi3O8)
Na SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
AlAluminium
Al BerylBe3Al2(Si6O18)
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al Beryl (var: Heliodor)Be3Al2(Si6O18)
Al AlbiteNa(AlSi3O8)
Al GahniteZnAl2O4
Al MicroclineK(AlSi3O8)
Al SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Al SpessartineMn32+Al2(SiO4)3
Al OrthoclaseK(AlSi3O8)
SiSilicon
Si BerylBe3Al2(Si6O18)
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si QuartzSiO2
Si Beryl (var: Heliodor)Be3Al2(Si6O18)
Si AlbiteNa(AlSi3O8)
Si BertranditeBe4(Si2O7)(OH)2
Si MicroclineK(AlSi3O8)
Si SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Si SpessartineMn32+Al2(SiO4)3
Si OrthoclaseK(AlSi3O8)
PPhosphorus
P FluorapatiteCa5(PO4)3F
P AutuniteCa(UO2)2(PO4)2 · 11H2O
KPotassium
K MuscoviteKAl2(AlSi3O10)(OH)2
K MicroclineK(AlSi3O8)
K OrthoclaseK(AlSi3O8)
CaCalcium
Ca FluorapatiteCa5(PO4)3F
Ca AutuniteCa(UO2)2(PO4)2 · 11H2O
MnManganese
Mn SpessartineMn32+Al2(SiO4)3
FeIron
Fe Limonite(Fe,O,OH,H2O)
Fe SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
ZnZinc
Zn GahniteZnAl2O4
NbNiobium
Nb Pyrochlore GroupA2Nb2(O,OH)6Z
TaTantalum
Ta Microlite GroupA2-mTa2X6-wZ-n
UUranium
U AutuniteCa(UO2)2(PO4)2 · 11H2O

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

Cambrian - Neoproterozoic
485.4 - 1000 Ma



ID: 3190533
Precambrian-Phanerozoic sedimentary and volcanic rocks

Age: Neoproterozoic to Cambrian (485.4 - 1000 Ma)

Lithology: Metasedimentary/metavolcanic schist

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]

Early Cambrian
511 - 541 Ma



ID: 2459559
Sykesville Formation

Age: Cambrian (511 - 541 Ma)

Stratigraphic Name: Sykesville Formation

Comments: brown; medium,thick bedded; clasts composed of metasedimentary rocks; Secondary tectonic (rotational) folation; feldspar; sedimentary melange, oceanic floor/trench; used for ornamental stone (ornamental)

Lithology: Conglomerate

Reference: Davis, A.M., C.S. Southworth, J.E. Reddy, J.S. Schindler. Geologic Map Database of the Washington DC Area Featuring Data from Three 30 x 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg. U.S. Geological Survey Open-File Report 01-227. [69]

Proterozoic
541 - 2500 Ma



ID: 3009292
Wissahickon Formation; Lower Pelitic Schist

Age: Proterozoic (541 - 2500 Ma)

Stratigraphic Name: Wissahickon Formation

Description: (Formerly mapped as oligoclase facies of Wissahickon Formation.) Medium- to coarse-grained biotite-oligoclase-muscovite-quartz schist with garnet, staurolite, and kyanite; fine- to medium-grained semipelitic schist; and fine-grained granular to weakly schistose psammitic granulite; psammitic beds increase upward; apparent thickness 5,500 feet or more.

Comments: Original map source: In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at http://www.mgs.md.gov/.

Lithology: Major:{biotite schist}, Minor:{granulite}

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

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Sterrett, D. B. (1923) Mica deposits of the United States: U. S. Geological Survey: Bulletin 740: 24, 104-105.
Shannon, E. V. (1926) Some minerals from the Kensington Mica Mine, Montgomery County, Maryland: American Mineralogist: 11: 35-37.
Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland 34.
Clayton Doak (April 30, 1976) Kensington-Gilmore Mica Mine: A description with emphasis on Interpretational Potential: University of Maryland Geology Department.
Bernstein, Lawrence (1980) Minerals of the Washington D. C. area: Maryland Geological Survey Educational Series 5, 148 p.


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