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Santa Cruz deposit (Casa Grande Santa Cruz deposit; Francisco Grande deposit; Fanny-Granny deposit; Franny-Granny deposit; Casa Grande; Casa Grande West), Casa Grande area, Casa Grande, Casa Grande District, Pinal Co., Arizona, USA

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Latitude & Longitude (WGS84): 32° 53' 25'' North , 111° 52' 35'' West
Latitude & Longitude (decimal): 32.89028,-111.87639
GeoHash:G#: 9tb7n5qpg
Locality type:Deposit
Köppen climate type:BWh : Hot deserts climate

A former underground Cu-Mo-Au-Ag deposit/prospect located in the center sec. 13 and sec. 24, T6S, R4E, and in sec. 19, T6S, R5E (Stanfield 7.5 minute topo map), about 7¼ miles W of Casa Grande proper (halfway between Casa Grande and Stanfield). Discovered 1976. Owned by the Casa Grande Copper Co.

Mineralization is a porphyry copper deposit. The ore zone is 2000 meters long, 800 meters wide, with a depth-to-top of 1600 meters and a thickness of 1700 meters. May be the largest atacamite deposit in the world. Ore control was intrusions and faulting.

The high grade of the ore body is due to a supergene enrichment zone composed of atacamite and chrysocolla in the oxide zone.

No production as yet, reserves proven for future open pit operations.

Regions containing this locality

Sonoran Desert, North America

Desert - 1,136 mineral species & varietal names listed

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

9 valid minerals.

Detailed Mineral List:

Formula: Cu2(OH)3Cl
Description: Principal supergene mineral; found in drill cores.
Reference: Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 121; Cook, S.S. (1988b), Petrologic studies of the supergene copper mineralization at the Santa cruz copper deposit, Pinal Co., AZ (abstract), Geol. Soc. Amer. Abs. with Progs. 20: A336.
Reference: Singer, D.A., Berger, V.I., and Moring, B.C. (2005): USGS Open-File Report 05-1060
Formula: Cu5FeS4
Reference: Singer, D.A., Berger, V.I., and Moring, B.C. (2005): USGS Open-File Report 05-1060
Formula: Cu2S
Reference: MRDS database Dep. ID #10097042, MRDS ID #M030493.
Formula: CuFeS2
Reference: MRDS database Dep. ID #10097042, MRDS ID #M030493.
Formula: Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Reference: MRDS database Dep. ID #10097042, MRDS ID #M030493.
Formula: CuS
Reference: MRDS database Dep. ID #10234953, MAS ID #0040210076.
Formula: MoS2
Reference: MRDS database Dep. ID #10097042, MRDS ID #M030493.
Formula: KAl2(AlSi3O10)(OH)2
Reference: Singer, D.A., Berger, V.I., and Moring, B.C. (2005): USGS Open-File Report 05-1060
Muscovite var: Sericite
Formula: KAl2(AlSi3O10)(OH)2
Reference: Singer, D.A., Berger, V.I., and Moring, B.C. (2005): USGS Open-File Report 05-1060
Formula: FeS2
Reference: MRDS database Dep. ID #10097042, MRDS ID #M030493.

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Group 3 - Halides
Group 9 - Silicates
'Chrysocolla'9.ED.20Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
var: Sericite9.EC.15KAl2(AlSi3O10)(OH)2
Unclassified Minerals, Rocks, etc.

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmBnXp, with (m+n):p = 2:1
AmBnXp, with (m+n):p = 3:2
AmXp, with m:p = 1:1
AmBnXp, with (m+n):p = 1:1
AmBnXp, with (m+n):p = 1:2
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Group 74 - PHYLLOSILICATES Modulated Layers
Modulated Layers with joined strips
Chrysocolla74.3.2.1Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Unclassified Minerals, Rocks, etc.
var: Sericite

List of minerals for each chemical element

H AtacamiteCu2(OH)3Cl
H ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
H MuscoviteKAl2(AlSi3O10)(OH)2
H Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
O AtacamiteCu2(OH)3Cl
O ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
O MuscoviteKAl2(AlSi3O10)(OH)2
O Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
Al ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
Si ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
S BorniteCu5FeS4
S ChalcociteCu2S
S ChalcopyriteCuFeS2
S CovelliteCuS
S MolybdeniteMoS2
S PyriteFeS2
Cl AtacamiteCu2(OH)3Cl
K MuscoviteKAl2(AlSi3O10)(OH)2
K Muscovite (var: Sericite)KAl2(AlSi3O10)(OH)2
Fe BorniteCu5FeS4
Fe ChalcopyriteCuFeS2
Fe PyriteFeS2
Cu AtacamiteCu2(OH)3Cl
Cu BorniteCu5FeS4
Cu ChalcociteCu2S
Cu ChalcopyriteCuFeS2
Cu ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Cu CovelliteCuS
Mo MolybdeniteMoS2

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

Holocene - Gelasian
0 - 2.588 Ma

ID: 2976496
Quaternary surficial deposits, undivided

Age: Pleistocene (0 - 2.588 Ma)

Description: Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)

Comments: 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:{sand,silt,clay}

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]

Quaternary - Miocene
0 - 23.03 Ma

ID: 3185380
Cenozoic sedimentary rocks

Age: Cenozoic (0 - 23.03 Ma)

Lithology: Sedimentary 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, used under Creative Commons Attribution 4.0 License


Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Greeley (1978) Arizona Department of Mineral Resources Special Report 2: 83-87.
Ullmer (1978) Journal of Geochemical Exploration: 9(2-3): 235-236.
Paydirt (1982) Casa Grande Copper Project on 'Back Shelf'. No. 522, Dec. 1982: 7.
Paydirt (1984) Getty Pays $10 Million for Land near Casa Grande Orebody: No. 541, July, 194: 21A-22A.
Cook, S.S. (1988b), Petrologic studies of the supergene copper mineralization at the Santa Cruz copper deposit, Pinal Co., Arizona (abstract), Geological Society of America Abstracts with Progs. 20: A336.
Mining Magazine (1988) In Situ Copper Mining Tests in U.S.A., December 1988: 460.
Ahlness and Millenacker (1989) Bureau of Mines Investigates i Situ Copper Mining Feb-Mar 1989: 9-15.
Dahl, Linda J. (1989) Summary Report - Casa Grande, American Mining Congress Journal, 2/89: 16.
Mining Journal, London (1989) Draft Mine Design, September 29, 1989.
The Mining Record (1990) ASARCO Takes Legal Action in Mining Research Venture, March 1990: 3.
Mining Engineering (1991) In Situ Copper Mining at Santa Cruz. A Project pdate, August 1991: 1031-1034.
Niemuth, N.J. & K.A. Phillips (1992), Copper Oxide Resources, AZ Dept. Mines & Min. Resources Open File Rept. 92-10: 15 (Table 1).
Paydirt (1992) Santa Cruz In Situ Copper Leacng Research ooking Good, february 1992: 3B (38 ?).
Sawyer, M.B., Gurmendi, A.C., Daley, M.R., and Howell, S.B. (1992) Principal Deposits of Strategic and Critical Minerals in Arizona, U.S. Bureau of Mines Special Publication, 334 pp.
American Mining Manual (1994) Copper Project gets green Light: 7.
Skillings Mining Review (1994) Arizona In Situ Miing Research Project Proceeds, November 26, 1994: 15.
Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 121.
Southwestern Paydirt (1995) Industry-Government Project has Big Potential, February, 1995: 4A-9A.
Mining Record (1996) Pilot-Scale Test Begins at Santa Cruz In Situ Project: 107(8), February 21, 1996: 4.
Singer, D.A., Berger, V.I., and Moring, B.C. (2005): Porphyry Copper Deposits of the World: Database, Map, and Grade and Tonnage Models. USGS Open-File Report 05-1060.
MRDS database Dep. ID #10097042, MRDS ID #M030493; and Dep. ID #10113316, MAS ID #0040211072; and Dep. ID #10234953, MRDS ID #TC35431, MAS ID #0040210076.

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