Vote for your favorite mineral in #MinCup26! - Cuprite vs. Orpiment
It's a fiery match of vibrant red Cuprite and just as saturated orange Orpiment battle for your votes!
Log InRegister
Quick Links : The Mindat ManualThe Rock H. Currier Digital LibraryMindat Newsletter [Free Download]
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 ArticlesThe ElementsThe Rock H. Currier Digital LibraryGeologic TimeExplore Fossils
Minerals by PropertiesMinerals by ChemistryMineral Visual ExplorerAdvanced 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 CompaniesStatisticsUsersMineral MuseumsClubs & OrganizationsMineral Shows & EventsThe Mindat DirectoryDevice SettingsThe Mineral QuizTime Machine
Photo SearchPhoto GalleriesSearch by ColorPhoto Colour ExplorerNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryPhotography

Folsom Mining District, Sacramento County, California, USAi
Regional Level Types
Folsom Mining DistrictMining District
Sacramento CountyCounty
CaliforniaState
USACountry

This page is currently not sponsored. Click here to sponsor this page.
PhotosMapsSearchMineralogy
03017870017272089544145.jpg
Native Gold

American River Placer deposit, Folsom, Folsom Mining District, Sacramento County, California, USA
03017870017272089544145.jpg
Native Gold

American River Placer deposit, Folsom, Folsom Mining District, Sacramento County, California, USA
03017870017272089544145.jpg
Native Gold

American River Placer deposit, Folsom, Folsom Mining District, Sacramento County, California, USA
Latitude & Longitude (WGS84):
38° North , 121° West (est.)
Estimate based on other nearby localities or region boundaries.
Margin of Error:
~64km
GRN:
N26W69
Type:
Mining District
Köppen climate type:
Csa : Hot-summer Mediterranean climate
Mindat Locality ID:
215845
Long-form identifier:
mindat:1:2:215845:0
GUID (UUID V4):
0


The Folsom District extends NW along the S side of the American River, S to Nimbus and W to Mather Air Force Base.

A Au-PGE (Pt-Ir) placer mining area. Pt from this district averages 43.49% Pt. Commonly ferroan platinum alloy and 20.81% Ir.

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.


Mineral List

Mineral list contains entries from the region specified including sub-localities

10 valid minerals.

Detailed Mineral List:

ⓘ Chromite
Formula: Fe2+Cr3+2O4
ⓘ 'Clay minerals'
Description: Refractory.
ⓘ Erlichmanite
Formula: OsS2
ⓘ Irarsite
Formula: (Ir,Ru,Rh,Pt)AsS
ⓘ 'Iron-Platinum alloy'
Formula: (Pt,Fe)
ⓘ Native Gold
Formula: Au
Localities: Reported from at least 17 localities in this region.
ⓘ Native Iridium
Formula: (Ir,Os,Ru)
ⓘ Native Iridium var. Osmiridium
Formula: (Ir,Os,Ru)
ⓘ Native Iridium var. Ruthenosmiridium
Formula: (Ir,Os,Ru)
ⓘ Native Osmium
Formula: (Os,Ir,Ru)
ⓘ Native Osmium var. Iridosmine
Formula: (Os,Ir)
ⓘ Native Platinum
Formula: Pt
Description: Placer material.
ⓘ Quartz
Formula: SiO2
Description: Fine quality.
ⓘ Quartz var. Rock Crystal
Formula: SiO2
Description: Fine quality.
ⓘ Rutheniridosmine
Formula: (Ir,Os,Ru)
ⓘ Sperrylite
Formula: PtAs2

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
ⓘNative Gold1.AA.05Au
ⓘNative Osmium1.AF.05(Os,Ir,Ru)
ⓘRutheniridosmine1.AF.05(Ir,Os,Ru)
ⓘNative Osmium
var. Iridosmine		1.AF.05(Os,Ir)
ⓘNative Iridium1.AF.10(Ir,Os,Ru)
ⓘNative Platinum1.AF.10Pt
ⓘNative Iridium
var. Ruthenosmiridium		1.AF.10(Ir,Os,Ru)
ⓘvar. Osmiridium1.AF.10(Ir,Os,Ru)
Group 2 - Sulphides and Sulfosalts
ⓘErlichmanite2.EB.05aOsS2
ⓘSperrylite2.EB.05aPtAs2
ⓘIrarsite2.EB.25(Ir,Ru,Rh,Pt)AsS
Group 4 - Oxides and Hydroxides
ⓘChromite4.BB.05Fe2+Cr3+2O4
ⓘQuartz4.DA.05SiO2
ⓘvar. Rock Crystal4.DA.05SiO2
Unclassified
ⓘ'Clay minerals'-
ⓘ'Iron-Platinum alloy'-(Pt,Fe)

List of minerals for each chemical element

OOxygen
Oⓘ ChromiteFe2+Cr23+O4
Oⓘ QuartzSiO2
Oⓘ Quartz var. Rock CrystalSiO2
SiSilicon
Siⓘ QuartzSiO2
Siⓘ Quartz var. Rock CrystalSiO2
SSulfur
Sⓘ ErlichmaniteOsS2
Sⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
CrChromium
Crⓘ ChromiteFe2+Cr23+O4
FeIron
Feⓘ ChromiteFe2+Cr23+O4
Feⓘ Iron-Platinum alloy(Pt,Fe)
AsArsenic
Asⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
Asⓘ SperrylitePtAs2
RuRuthenium
Ruⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
Ruⓘ Native Iridium(Ir,Os,Ru)
Ruⓘ Native Osmium(Os,Ir,Ru)
Ruⓘ Rutheniridosmine(Ir,Os,Ru)
Ruⓘ Native Iridium var. Ruthenosmiridium(Ir,Os,Ru)
Ruⓘ Native Iridium var. Osmiridium(Ir,Os,Ru)
RhRhodium
Rhⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
OsOsmium
Osⓘ ErlichmaniteOsS2
Osⓘ Native Iridium(Ir,Os,Ru)
Osⓘ Native Osmium(Os,Ir,Ru)
Osⓘ Rutheniridosmine(Ir,Os,Ru)
Osⓘ Native Iridium var. Ruthenosmiridium(Ir,Os,Ru)
Osⓘ Native Iridium var. Osmiridium(Ir,Os,Ru)
Osⓘ Native Osmium var. Iridosmine(Os,Ir)
IrIridium
Irⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
Irⓘ Native Iridium(Ir,Os,Ru)
Irⓘ Native Osmium(Os,Ir,Ru)
Irⓘ Rutheniridosmine(Ir,Os,Ru)
Irⓘ Native Iridium var. Ruthenosmiridium(Ir,Os,Ru)
Irⓘ Native Iridium var. Osmiridium(Ir,Os,Ru)
Irⓘ Native Osmium var. Iridosmine(Os,Ir)
PtPlatinum
Ptⓘ Iron-Platinum alloy(Pt,Fe)
Ptⓘ Irarsite(Ir,Ru,Rh,Pt)AsS
Ptⓘ Native PlatinumPt
Ptⓘ SperrylitePtAs2
AuGold
Auⓘ Native GoldAu

Localities in this Region

USA
USA

Other Regions, Features and Areas containing this locality

North AmericaContinent
North America PlateTectonic Plate

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.

References

Logan, C. A. (1919) Platinum and Allied Metals in California. Bulletin 85. California State Mining Bureaupages 27-28, 109
Clark, W.B. (1970) Gold Districts of California. Bulletin 193. California Division of Mines & Geology
Clark, Wm. B. (1970b) Platinum: California Division Mines and Geology Mineral Information Service: 23: 115-122:
Pemberton, H. Earl (1983) Minerals of California. Van Nostrand Reinhold Company Inc.
Quick NavTopCommoditiesMineral ListLocalities in RegionOther RegionsReferences
 
and/or  
Mindat.org® is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Mindat® and mindat.org® are registered trademarks of the Hudson Institute of Mineralogy.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2026, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph and Ida Chau.
Content on this site may not be used to train, fine-tune, or otherwise develop artificial intelligence or machine learning models without prior written permission - see our Terms & Conditions.
To cite: Ralph, J., Von Bargen, D., Martynov, P., Zhang, J., Que, X., Prabhu, A., Morrison, S. M., Li, W., Chen, W., & Ma, X. (2025). Mindat.org: The open access mineralogy database to accelerate data-intensive geoscience research. American Mineralogist, 110(6), 833–844. doi:10.2138/am-2024-9486.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: September 5, 2026 14:57:39 Page updated: July 27, 2026 04:11:30
Go to top of page