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Alto Mine (Alto vein; Gold Tree Mine; El Plomo Mine), Alto Mine group (Alto vein swarm), Alto Hill, Salero area, Tyndall District, Santa Rita Mts, Santa Cruz Co., Arizona, USAi
Regional Level Types
Alto Mine (Alto vein; Gold Tree Mine; El Plomo Mine)Mine
Alto Mine group (Alto vein swarm)- not defined -
Alto HillHill
Salero areaArea
Tyndall DistrictMining District
Santa Rita MtsMountain Range
Santa Cruz Co.County
ArizonaState
USACountry

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Key
Lock Map
Latitude & Longitude (WGS84):
31° 36' 41'' North , 110° 51' 39'' West
Latitude & Longitude (decimal):
Locality type:
Nearest Settlements:
PlacePopulationDistance
Patagonia890 (2017)12.7km
Tubac1,191 (2011)17.5km
Tumacacori-Carmen393 (2015)18.0km
Rio Rico18,962 (2011)19.0km
Sonoita818 (2015)20.7km


‡Ref.: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 200-203.

Tenney, J.B. (1927-1929) History of Mining in Arizona, Special Collection, University of Arizona Library & Arizona Bureau of Mines Library: 315-316.

U.S. Atomic Energy Commission Preliminary Reconnaissance Report A-P-360 & 11 (1955).

Drewes, H.D. (1971) Geologic map of the Mount Wrightson quadrangle, southeast of Tucson, Santa Cruz and Pima Counties, Arizona: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-614, 1 sheet, scale 1:48,000.

Drewes, H.D., 1972, Cenozoic rocks of the Santa Rita Mountains, southeast of Tucson, Arizona: U.S. Geological Survey Professional Paper 746, 66 p.

Drewes, H.D., 1973, Geochemical reconnaissance of the Santa Rita Mountains, southeast of Tucson, Arizona: U.S. Geological Survey Bulletin 1365, 67 p., 2 sheets, scale 1:24,000.

Keith, Stanton B. (1975) State of Arizona Bureau of Geology and Mineral Technology, Geological Survey Branch Bull. 191, Index of Mining Properties in Santa Cruz County, Arizona.

U.S. Bureau of Land Management Mining District Sheet 668.

U.S. Bureau of Mines - Arizona Bureau of Geology and Mineral Technology file data.

U.S. Bureau of Mines file data, Alto Mine Group file.

MRDS database Dep. ID file #10037106, MRDS ID #M030411.

A former small underground Pb-Ag-Zn-Au-Cu-Mo-Sb-Baryte-U mine located on 13 unpatented claims. in the S½ sec. 12 & the N½ sec. 13, T21S, R14E, 2.5 miles N of Salero, about 1/2 mile NW of the Lineboy Mine, 3/4 mile NW of the Boundary post 113 on the Mexican border, on private land. Discovered in 1687 by Jesuit priests of the Tumacacori missionaries. Relocated by Americans in 1873 as the Gold Tree Mine. Produced from 1687 to 1959. Owned by R. R Hansen and Associates (1965). Operated by the Fortuna Mining Co. (1956).

Mineralization is the Alto vein which lies in latite and granite porphyry and contains most of the development work of the mine as a whole. It extends through a length of two or more claims and is from 3 to 7 feet wide. The average dip of this vein for the first 300 feet in depth is about vertical.

An auxiliary, or blind, vein dipping steeply to the north or vertical comes in from the WSW about 400 feet into the tunnel. This blind vein contains principally galena, sphalerite and other sulfides. Between 600 and 800 feet from the portal another small vein dipping steeply to the north contains chalcopyrite ore. Between the 1,400 and 1,560 feet in a large body of kaolin or gouge occurs and the vein is 6 feet wide. From the 800 foot point to the face of the tunnel the vein carries a more or less continuous 18 inch (45 cm) oreshoot in which the ore occurs in lenses and stringers of galena, 6 inches (15 cm) or more in maximum width. At the face of the tunnel the vein is about 4 feet wide and contains an ore shoot nearly a foot wide in the north or hanging wall side, the rest of the width consisting mostly of altered rock carrying sulphide ore minerals all the way across. The middle part of the vein in this portion of the mine is said to carry generally considerable sphalerite.

Ore control was tension fractures; six E-W-trending quartz fissure veins, mainly in La Tite and granite porphyry. Ore concentration was supergene enrichement and oxidation near surface. Alteration is kaolinization in fault gouge. Associated rock units are the Salero Formation; the Jospehine Canyon Diorite and the Squaw Peak Granite.

Local structures include E-W and NE-trending quartz fissure veins along contacts and fault zones in diorite and granite porphyry. The veins are generally well-defined, carrying ore shoots. Tectonic elements include the Salero Fault Block.

The main vein is opened by the 1,632 foot long Alto tunnel with connecting shafts. The blind vein is opened by a back drift known as the west drift, for 130 feet to the west. Most shafts are flooded. Operations included a 300 foot vertical shaft, 2000 & 1400 foot adits, a 175 foot deep vertical shaft with 200 feet of raise, and a 90 foot inclined shaft. Workings total 3048 meters in length and 67.06 meters in depth.

Regions containing this locality

North America PlateTectonic Plate
Sonoran Desert, North AmericaDesert

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List


15 valid minerals.

Detailed Mineral List:

Acanthite
Formula: Ag2S
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 202.
Baryte
Formula: BaSO4
Reference: MRDS database Dep. ID file #10037106, MRDS ID #M030411.
Calcite
Formula: CaCO3
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 202.
Chalcocite
Formula: Cu2S
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 202.
Chalcopyrite
Formula: CuFeS2
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 203.
Galena
Formula: PbS
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 200-203.
Hematite
Formula: Fe2O3
Reference: MRDS database Dep. ID file #10037106, MRDS ID #M030411.
Kaolinite
Formula: Al2(Si2O5)(OH)4
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 200-201.
Malachite
Formula: Cu2(CO3)(OH)2
Reference: MRDS database Dep. ID file #10037106, MRDS ID #M030411.
Molybdenite
Formula: MoS2
Reference: MRDS database Dep. ID file #10037106, MRDS ID #M030411.
Pyrite
Formula: FeS2
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 202.
Sphalerite
Formula: ZnS
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 200-203.
Tenorite
Formula: CuO
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 203.
Tetrahedrite
Formula: Cu6[Cu4(Fe,Zn)2]Sb4S13
Reference: Schrader, F.C. & J.M. Hill (1915), Mineral deposits of the Santa Rita and Patagonia Mountains, Arizona, USGS Bull. 582: 202.
Uraninite
Formula: UO2
Reference: MRDS database Dep. ID file #10037106, MRDS ID #M030411.

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Acanthite2.BA.35Ag2S
Chalcocite2.BA.05Cu2S
Chalcopyrite2.CB.10aCuFeS2
Galena2.CD.10PbS
Molybdenite2.EA.30MoS2
Pyrite2.EB.05aFeS2
Sphalerite2.CB.05aZnS
Tetrahedrite2.GB.05Cu6[Cu4(Fe,Zn)2]Sb4S13
Group 4 - Oxides and Hydroxides
Hematite4.CB.05Fe2O3
Tenorite4.AB.10CuO
Uraninite4.DL.05UO2
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3
Malachite5.BA.10Cu2(CO3)(OH)2
Group 7 - Sulphates, Chromates, Molybdates and Tungstates
Baryte7.AD.35BaSO4
Group 9 - Silicates
Kaolinite9.ED.05Al2(Si2O5)(OH)4

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmBnXp, with (m+n):p = 2:1
Acanthite2.4.1.1Ag2S
Chalcocite2.4.7.1Cu2S
AmXp, with m:p = 1:1
Galena2.8.1.1PbS
Sphalerite2.8.2.1ZnS
AmBnXp, with (m+n):p = 1:1
Chalcopyrite2.9.1.1CuFeS2
AmBnXp, with (m+n):p = 1:2
Molybdenite2.12.10.1MoS2
Pyrite2.12.1.1FeS2
Group 3 - SULFOSALTS
3 <ø < 4
Tetrahedrite3.3.6.1Cu6[Cu4(Fe,Zn)2]Sb4S13
Group 4 - SIMPLE OXIDES
AX
Tenorite4.2.3.1CuO
A2X3
Hematite4.3.1.2Fe2O3
Group 5 - OXIDES CONTAINING URANIUM OR THORIUM
AXO2·xH2O
Uraninite5.1.1.1UO2
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Group 16a - ANHYDROUS CARBONATES CONTAINING HYDROXYL OR HALOGEN
Malachite16a.3.1.1Cu2(CO3)(OH)2
Group 28 - ANHYDROUS ACID AND NORMAL SULFATES
AXO4
Baryte28.3.1.1BaSO4
Unclassified Minerals, Mixtures, etc.
Kaolinite-Al2(Si2O5)(OH)4

List of minerals for each chemical element

HHydrogen
H KaoliniteAl2(Si2O5)(OH)4
H MalachiteCu2(CO3)(OH)2
CCarbon
C CalciteCaCO3
C MalachiteCu2(CO3)(OH)2
OOxygen
O KaoliniteAl2(Si2O5)(OH)4
O CalciteCaCO3
O TenoriteCuO
O HematiteFe2O3
O MalachiteCu2(CO3)(OH)2
O BaryteBaSO4
O UraniniteUO2
AlAluminium
Al KaoliniteAl2(Si2O5)(OH)4
SiSilicon
Si KaoliniteAl2(Si2O5)(OH)4
SSulfur
S GalenaPbS
S SphaleriteZnS
S TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
S PyriteFeS2
S AcanthiteAg2S
S ChalcociteCu2S
S ChalcopyriteCuFeS2
S MolybdeniteMoS2
S BaryteBaSO4
CaCalcium
Ca CalciteCaCO3
FeIron
Fe TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
Fe PyriteFeS2
Fe ChalcopyriteCuFeS2
Fe HematiteFe2O3
CuCopper
Cu TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
Cu ChalcociteCu2S
Cu TenoriteCuO
Cu ChalcopyriteCuFeS2
Cu MalachiteCu2(CO3)(OH)2
ZnZinc
Zn SphaleriteZnS
Zn TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
MoMolybdenum
Mo MolybdeniteMoS2
AgSilver
Ag AcanthiteAg2S
SbAntimony
Sb TetrahedriteCu6[Cu4(Fe,Zn)2]Sb4S13
BaBarium
Ba BaryteBaSO4
PbLead
Pb GalenaPbS
UUranium
U UraniniteUO2

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

Miocene - Oligocene
5.333 - 33.9 Ma



ID: 3184329
Cenozoic volcanic rocks

Age: Cenozoic (5.333 - 33.9 Ma)

Comments: Sierra Madre Occidental

Lithology: Ignimbrite(s); felsic volcanic 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]

Ypresian - Campanian
47.8 - 83.6 Ma



ID: 2775064
Early Tertiary to Late Cretaceous granitic rocks

Age: Phanerozoic (47.8 - 83.6 Ma)

Description: Porphyritic to equigranular granite to diorite emplaced during the Laramide orogeny. Larger plutons are characteristically medium-grained, biotite +/- hornblende granodiorite to granite. Smaller, shallow-level intrusions are typically porphyritic. Most of the large copper deposits in Arizona are associated with porphyritic granitic rocks of this unit, and are thus named 'porphyry copper deposits'. (50-82 Ma)

Comments: Laramide metaluminous; associated with porphyry Cu deposits Original map source: Arizona Geological Survey, DI-8 Geologic Map of Arizona, Digital Spatial data for the Geologic Map of Arizona, v. 3.0, edited by S.M. Richard and S.M. Kneale, 2002, 10 p., 2 DOS HD disks. Arc/INFO export file (.e00) format, scale 1:1,000,000.

Lithology: Major:{granite,granodiorite,diorite}

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

USGS MRDS Record:10037106
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