Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat Articles
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
Keyword(s):
 
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsThe ElementsUsersBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

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

This page is currently not sponsored. Click here to sponsor this page.
Key
Lock Map
Latitude & Longitude (WGS84): 33° 12' 23'' North , 116° 47' 54'' West
Latitude & Longitude (decimal): 33.20639,-116.79833
GeoHash:G#: 9muuyjn11
Locality type:Mine
Köppen climate type:Csa : Hot-summer Mediterranean climate
Nearest Settlements:
PlacePopulationDistance
San Pasqual2,041 (2018)19.3km
Ramona20,292 (2011)19.4km
Valley Center9,277 (2011)22.0km
Hidden Trails750 (2008)22.2km
San Diego Country Estates10,109 (2011)22.2km


At the gambling table, there are no fathers and sons.
-Chinese proverb.

Setting:
The Mesa Grande mine is located near the center of the N/2 Sec 20, T11S, R2E, SBM, nearly 2.5 miles (4 km) northwest of Mesa Grande on the steep east slope of Gem Hill within the boundaries of the DeForest Ranch property, located immediately adjacent to the Angel Ranch property. Livestock raising activities have traditionally dominated the use of surrounding lands, and although conflicts between ranchers and miners occasionally erupt over mineral rights, local ranch hands have played an important part in the development of the gemstone resources in the area.

Geology:
The geology of the Mesa Grande mine consists of a local series of three continuous pegmatite dikes averaging 2 to 4 feet in thickness, enclosed within a well-defined gabbroic micropluton. These dikes follow a general north to northwest strike and display an average dip of between 20 and 35 degrees west to southwest. These vein-like bodies are clearly exposed and traceable along the available surface exposure and should be considered prominent southern extensions of the productive Himalaya dike system. The gem-bearing portions of the deposit are located within the central portions of these dikes, characterized as quartz-subhedral perthite pegmatite forming distinctly localized areas of abnormally enlarged crystal structure.

History:
The Mesa Grande mine workings were reported to have originally opened sometime between 1903 and 1904, by the Mesa Grande Tourmaline and Gem Company. The officers of the company were: President, Frank A. Seabert, whom spent a large portion of his time at the property; Vice-President, Horace Wilson, a well known business man of Los Angeles; Superintendent, C. O. McCarroll, pioneering California gemologist; Secretary, H. E. Felkenson of Southwestern Securities Company; and Los Angeles Banker, Frank A Liddell. The mine yielded a modest amount of pink and purple tourmaline, beryl (aquamarine and goshenite), and quartz (white and smoky). At least 1100 carats of tourmaline gems were reported to have been cut and sold. The principal development during this period was a cut 60 feet long, 15 to 40 feet wide, and 25 feet deep. From this main cut was driven an adit which extended 80 feet underground into the mountain, cutting through the first two dikes, at which point an appended drift followed the southernmost pegmatite to the northwest for nearly 180 feet. Other cuts and minor adits were driven along the surface outcroppings of the three main dikes, extending down dip no greater than 20 feet. Work on the property by the company had ceased around 1910.

Recent Activities:
In November of 1995, several parties involved in consolidation of various gem-bearing properties on Gem Hill began surface reconnaissance and detailed exploration of the Mesa Grande mine. The original mine workings had recently been partly uncovered by the land owner's ranch laborers, so it was decided that work should be focused at these locations. Field work was primarily conducted by Erik Cordova and Scott Ritchie of the San Diego Mining Company.

At this point in time, and apparently since 1957, existing underground workings had become inaccessible due to ongoing caving of decomposed pegmatite and gabbro. Some small pink tourmalines of gem quality were discovered on the brush-covered dumps of the lower, northernmost adit. Additional exploration along the surface exposure of the upper, southernmost pegmatite occurred for a period of 4 weeks.

Within the second week of exploration, Cordova discovered signs of a large gem bearing pocket and began to systematically excavate at the point of discovery. With the weather being exceedingly both cold and wet, work upon the surface was stopped prematurely - although not before several days of digging had unearthed several large smoky quartz crystals nearly a foot in length, as well as several kilos of fine gem-schorl prisms measuring up to 7 inches in length. Additionally, many fine spessartine nodules of exceptional orange color and of top facet quality were recovered. The largest of these crystals was nearly "golf ball" sized in its proportions. Some of these fine garnet crystals were also found on an aesthetic matrix of microcline and cleavelandite accented by cookeite, making for attractive mineral specimens.

Several hundred kilos of quartz crystals, a dozen kilos of slender black tourmaline (schorl) crystals, and three kilos of deep orange garnets (spessartine) were recovered. In all, over forty buckets (5 gallon capacity) of water screened pocket material were taken out. Unfortunately, most of this material was stolen by a self-proclaimed "gemstone mining expert" — a con man from Arizona unwittingly hired by the mine owner to ensure equity of the bonanza. Several months later, a pale pink beryl crystal (var. morganite) measuring approximately 2 inches across was found on the dumps by one of the miners from the nearby Himalaya mine. It was apparent that much gem-material was lost during the ensuing frenzy, having been hastily excavated and pushed over the edge with the backhoe in a mad rush to empty the pocket.

Regions containing this locality

Pacific PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List


8 valid minerals.

Detailed Mineral List:

Albite
Formula: Na(AlSi3O8)
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
Albite var: Cleavelandite
Formula: Na(AlSi3O8)
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
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: 309 p., illus., maps.
Beryl var: Aquamarine
Formula: Be3Al2Si6O18
Reference: Weber, F. H. 1963. Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: 309 p., illus., maps.
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: 309 p., illus., maps.
Beryl var: Morganite
Formula: Be3Al2(Si6O18)
Reference: Larson, W. F. 1996. Personal communication between Scott L. Ritchie and William F. Larson; underground inspection of recent development works and beryl recovery on the dumps of the Mesa Grande mine by Montes, B.; Spring.
Elbaite
Formula: Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
'Lepidolite'
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
Microcline
Formula: K(AlSi3O8)
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
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: 309 p., illus., maps.
Quartz var: Smoky 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: 309 p., illus., maps.
'Rubellite'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Reference: Mesa Grande Tourmaline & Gem Company 1906. Do It Now!! Buy Tourmaline Stock; The Pacific Monthly, Advertisement Section, January 1906. The Pacific Monthly Publishing Co.; Portland, Oregon.
Schorl
Formula: Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
Spessartine
Formula: Mn2+3Al2(SiO4)3
Reference: San Diego Mining Company 1996. Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.
'Tourmaline'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Reference: Mesa Grande Tourmaline & Gem Company 1906. Do It Now!! Buy Tourmaline Stock; The Pacific Monthly, Advertisement Section, January 1906. The Pacific Monthly Publishing Co.; Portland, Oregon.
'Verdelite'
Formula: A(D3)G6(T6O18)(BO3)3X3Z
Reference: Mesa Grande Tourmaline & Gem Company 1906. Do It Now!! Buy Tourmaline Stock; The Pacific Monthly, Advertisement Section, January 1906. The Pacific Monthly Publishing Co.; Portland, Oregon.

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: Aquamarine9.CJ.05Be3Al2Si6O18
var: Goshenite9.CJ.05Be3Al2(Si6O18)
var: Morganite9.CJ.05Be3Al2(Si6O18)
Elbaite9.CK.05Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Microcline9.FA.30K(AlSi3O8)
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
Schorl9.CK.05Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Spessartine9.AD.25Mn2+3Al2(SiO4)3
Unclassified Minerals, Rocks, etc.
'Lepidolite'-
'Rubellite'-A(D3)G6(T6O18)(BO3)3X3Z
'Tourmaline'-A(D3)G6(T6O18)(BO3)3X3Z
'Verdelite'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals arranged by Dana 8th Edition classification

Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in [6] and >[6] coordination
Spessartine51.4.3a.3Mn2+3Al2(SiO4)3
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)
Microcline76.1.1.5K(AlSi3O8)
Unclassified Minerals, Mixtures, etc.
Albite
var: Cleavelandite
-Na(AlSi3O8)
Beryl
var: Aquamarine
-Be3Al2Si6O18
var: Goshenite-Be3Al2(Si6O18)
var: Morganite-Be3Al2(Si6O18)
'Lepidolite'-
Quartz
var: Smoky Quartz
-SiO2
'Rubellite'-A(D3)G6(T6O18)(BO3)3X3Z
'Tourmaline'-A(D3)G6(T6O18)(BO3)3X3Z
'Verdelite'-A(D3)G6(T6O18)(BO3)3X3Z

List of minerals for each chemical element

HHydrogen
H SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
H ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
H MuscoviteKAl2(AlSi3O10)(OH)2
LiLithium
Li ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
BeBeryllium
Be Beryl (var: Aquamarine)Be3Al2Si6O18
Be BerylBe3Al2(Si6O18)
Be Beryl (var: Goshenite)Be3Al2(Si6O18)
Be Beryl (var: Morganite)Be3Al2(Si6O18)
BBoron
B TourmalineA(D3)G6(T6O18)(BO3)3X3Z
B SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
B RubelliteA(D3)G6(T6O18)(BO3)3X3Z
B VerdeliteA(D3)G6(T6O18)(BO3)3X3Z
B ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
OOxygen
O TourmalineA(D3)G6(T6O18)(BO3)3X3Z
O Beryl (var: Aquamarine)Be3Al2Si6O18
O BerylBe3Al2(Si6O18)
O SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
O RubelliteA(D3)G6(T6O18)(BO3)3X3Z
O VerdeliteA(D3)G6(T6O18)(BO3)3X3Z
O ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
O Beryl (var: Goshenite)Be3Al2(Si6O18)
O Beryl (var: Morganite)Be3Al2(Si6O18)
O QuartzSiO2
O Quartz (var: Smoky Quartz)SiO2
O MicroclineK(AlSi3O8)
O Albite (var: Cleavelandite)Na(AlSi3O8)
O SpessartineMn32+Al2(SiO4)3
O MuscoviteKAl2(AlSi3O10)(OH)2
O AlbiteNa(AlSi3O8)
NaSodium
Na SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Na ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Na Albite (var: Cleavelandite)Na(AlSi3O8)
Na AlbiteNa(AlSi3O8)
AlAluminium
Al Beryl (var: Aquamarine)Be3Al2Si6O18
Al BerylBe3Al2(Si6O18)
Al SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Al ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Al Beryl (var: Goshenite)Be3Al2(Si6O18)
Al Beryl (var: Morganite)Be3Al2(Si6O18)
Al MicroclineK(AlSi3O8)
Al Albite (var: Cleavelandite)Na(AlSi3O8)
Al SpessartineMn32+Al2(SiO4)3
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al AlbiteNa(AlSi3O8)
SiSilicon
Si Beryl (var: Aquamarine)Be3Al2Si6O18
Si BerylBe3Al2(Si6O18)
Si SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Si ElbaiteNa(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)
Si Beryl (var: Goshenite)Be3Al2(Si6O18)
Si Beryl (var: Morganite)Be3Al2(Si6O18)
Si QuartzSiO2
Si Quartz (var: Smoky Quartz)SiO2
Si MicroclineK(AlSi3O8)
Si Albite (var: Cleavelandite)Na(AlSi3O8)
Si SpessartineMn32+Al2(SiO4)3
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si AlbiteNa(AlSi3O8)
KPotassium
K MicroclineK(AlSi3O8)
K MuscoviteKAl2(AlSi3O10)(OH)2
MnManganese
Mn SpessartineMn32+Al2(SiO4)3
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)
Mesa Grande Tourmaline & Gem Company (1906), Do It Now!! Buy Tourmaline Stock; The Pacific Monthly, Advertisement Section, January 1906. The Pacific Monthly Publishing Co.; Portland, Oregon.
Weber, F. H. (1963a), Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: 309 p., illus., maps.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 448 (map 13-1).
Larson, W. F. (1996), Personal communication between Scott L. Ritchie and William F. Larson; underground inspection of recent development works and beryl recovery on the dumps of the Mesa Grande mine by Montes, B.; Spring.
San Diego Mining Company (1996), Gem Hill exploration program; Cordova, E. M., Ritchie, S. L., Rose, C. H., Wilson, R.; Mesa Grande mine field analysis and valuable mineral discovery, Winter 1995-96.


This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2019, except where stated. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: March 21, 2019 18:19:53 Page generated: March 21, 2019 15:11:40
Go to top of page