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Cota Mine, Gem Hill, Mesa Grande District, San Diego Co., California, USAi
Regional Level Types
Cota MineMine
Gem HillHill
Mesa Grande DistrictMining District
San Diego Co.County
CaliforniaState
USACountry

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Latitude & Longitude (WGS84):
33° 12' 22'' North , 116° 48' 28'' West
Latitude & Longitude (decimal):
Locality type:
Nearest Settlements:
PlacePopulationDistance
San Pasqual2,041 (2018)18.6km
Ramona20,292 (2011)19.1km
Valley Center9,277 (2011)21.1km
Hidden Trails750 (2008)21.3km
San Diego Country Estates10,109 (2011)22.3km


Located near the center SE¼NE¼ sec. 19, T11S, R2E, SBM, approximately 3 miles northwest of Mesa Grande, on the west slope of Gem Hill. Ownership was undetermined in 1957.

The deposit is a pegmatite dike which strikes northwest and dips gently southwest, which ranges in thickness from 2 to 5 feet. Gem minerals were mined from pockets in pods of quartz euhedral perthite pegmatite exposed as discontinuous core segments. Pockets exposed around 1957 were 2 inches or less in maximum dimension and lined with small crystals of quartz, muscovite, albite, and colorless to pale pink beryl. Coarse cleavelandite and lepidolite were present in the dump.

The deposit was discovered in 1907 by Juan Mario Cota, who developed the mine between 1907 and 1910. These workings were reported to have produced garnet, beryl and tourmaline of several shades including amber and wine color. Total output of gem minerals may have been as much as 500 pounds. These workings which were largely overgrown by 1957, consisted of a cut approximately 50 feet long, 10 to 25 feet wide, and 5 to 12 feet deep.

Regions containing this locality

Pacific OceanOcean
Pacific PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List


6 valid minerals.

Detailed Mineral List:

Albite
Formula: Na(AlSi3O8)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Albite var: Cleavelandite
Formula: Na(AlSi3O8)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Beryl
Formula: Be3Al2(Si6O18)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Beryl var: Goshenite
Formula: Be3Al2(Si6O18)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Beryl var: Morganite
Formula: Be3Al2(Si6O18)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Elbaite
Formula: Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Elbaite-Schorl Series'
Reference: Pala International collection, 2003.
'Feldspar Group'
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Feldspar Group var: Perthite'
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Garnet Group'
Formula: X3Z2(SiO4)3
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Lepidolite'
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Mica Group'
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Quartz
Formula: SiO2
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Quartz var: Smoky Quartz
Formula: SiO2
Reference: Russ Rizzo
Schorl
Formula: Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Tourmaline'
Formula: A(D3)G6(Si6O18)(BO3)3X3Z
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Tourmaline var: Rubellite'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
'Tourmaline var: Verdelite'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Quartz4.DA.05SiO2
var: Smoky Quartz4.DA.05SiO2
Group 9 - Silicates
Albite9.FA.35Na(AlSi3O8)
var: Cleavelandite9.FA.35Na(AlSi3O8)
Beryl9.CJ.05Be3Al2(Si6O18)
var: Goshenite9.CJ.05Be3Al2(Si6O18)
var: Morganite9.CJ.05Be3Al2(Si6O18)
Elbaite9.CK.05Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
Schorl9.CK.05Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Unclassified Minerals, Rocks, etc.
'Elbaite-Schorl Series'-
'Feldspar Group'-
'var: Perthite'-
'Garnet Group'-X3Z2(SiO4)3
'Lepidolite'-
'Mica Group'-
'Tourmaline'-A(D3)G6(Si6O18)(BO3)3X3Z
'var: Rubellite'-A(D3)G6(T6O18)(BO3)3X3Z
'var: Verdelite'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals arranged by Dana 8th Edition classification

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
Elbaite61.3.1.8Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
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)
Unclassified Minerals, Mixtures, etc.
var: Cleavelandite-Na(AlSi3O8)
Beryl
var: Goshenite
-Be3Al2(Si6O18)
var: Morganite-Be3Al2(Si6O18)
'Elbaite-Schorl Series'-
'Feldspar Group'-
'var: Perthite'-
'Garnet Group'-X3Z2(SiO4)3
'Lepidolite'-
'Mica Group'-
Quartz
var: Smoky Quartz
-SiO2
'Tourmaline'-A(D3)G6(Si6O18)(BO3)3X3Z
'var: Rubellite'-A(D3)G6(T6O18)(BO3)3X3Z
'var: Verdelite'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals for each chemical element

HHydrogen
H MuscoviteKAl2(AlSi3O10)(OH)2
H ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
H SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
LiLithium
Li ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
BeBeryllium
Be Beryl (var: Goshenite)Be3Al2(Si6O18)
Be Beryl (var: Morganite)Be3Al2(Si6O18)
Be BerylBe3Al2(Si6O18)
BBoron
B TourmalineA(D3)G6(Si6O18)(BO3)3X3Z
B ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
B SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
B Tourmaline (var: Rubellite)A(D3)G6(T6O18)(BO3)3X3Z
B Tourmaline (var: Verdelite)A(D3)G6(T6O18)(BO3)3X3Z
OOxygen
O QuartzSiO2
O MuscoviteKAl2(AlSi3O10)(OH)2
O AlbiteNa(AlSi3O8)
O Beryl (var: Goshenite)Be3Al2(Si6O18)
O Beryl (var: Morganite)Be3Al2(Si6O18)
O BerylBe3Al2(Si6O18)
O Albite (var: Cleavelandite)Na(AlSi3O8)
O Garnet GroupX3Z2(SiO4)3
O TourmalineA(D3)G6(Si6O18)(BO3)3X3Z
O ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
O SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
O Tourmaline (var: Rubellite)A(D3)G6(T6O18)(BO3)3X3Z
O Tourmaline (var: Verdelite)A(D3)G6(T6O18)(BO3)3X3Z
O Quartz (var: Smoky Quartz)SiO2
NaSodium
Na AlbiteNa(AlSi3O8)
Na Albite (var: Cleavelandite)Na(AlSi3O8)
Na ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Na SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
AlAluminium
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al AlbiteNa(AlSi3O8)
Al Beryl (var: Goshenite)Be3Al2(Si6O18)
Al Beryl (var: Morganite)Be3Al2(Si6O18)
Al BerylBe3Al2(Si6O18)
Al Albite (var: Cleavelandite)Na(AlSi3O8)
Al ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Al SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
SiSilicon
Si QuartzSiO2
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si AlbiteNa(AlSi3O8)
Si Beryl (var: Goshenite)Be3Al2(Si6O18)
Si Beryl (var: Morganite)Be3Al2(Si6O18)
Si BerylBe3Al2(Si6O18)
Si Albite (var: Cleavelandite)Na(AlSi3O8)
Si Garnet GroupX3Z2(SiO4)3
Si TourmalineA(D3)G6(Si6O18)(BO3)3X3Z
Si ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Si SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Si Quartz (var: Smoky Quartz)SiO2
KPotassium
K MuscoviteKAl2(AlSi3O10)(OH)2
FeIron
Fe SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)

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

Cretaceous - Triassic
66 - 251.902 Ma



ID: 2791019
Mesozoic gabbroic rocks, unit 2 (undivided)

Age: Mesozoic (66 - 251.902 Ma)

Stratigraphic Name: Cuyamaca Gabbro; Elk Creek Gabbro; Gold Park Gabbro-Diorite; San Marcos Gabbro; Summit Gabbro

Description: Gabbro and dark dioritic rocks; chiefly Mesozoic

Comments: Mostly small exposures of gabbro and diorite scattered in western Klamath Mts., Sierra Nevada, Coast Ranges, Mojave Desert, and Peninsular Ranges Original map source: Saucedo, G.J., Bedford, D.R., Raines, G.L., Miller, R.J., and Wentworth, C.M., 2000, GIS Data for the Geologic Map of California, California Department of Conservation, Division of Mines and Geology, CD-ROM 2000-07, scale 1:750,000.

Lithology: Major:{diorite,gabbro}

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]

Cretaceous
66 - 145 Ma



ID: 3186295
Mesozoic intrusive rocks

Age: Cretaceous (66 - 145 Ma)

Lithology: Intrusive igneous rocks

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]

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)
Weber, F.H. (1963a) Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: p. 100.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 448.


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