Geology of the Mule Mountains
                                  and Bisbee

Cochise College                                             
Geology of Southeastern Arizona
Geology Home Page

Roger Weller, geology instructor    last edited:  10/11/16

Juniper Flats in the Mule Mountains, Cochise County, Arizona


Mule Mountains and Bisbee


general geology

Bisbee (from: Ransome, USGS Folio, 1914)


“The town of Bisbee, with an estimated population of 8,000, is crowded into a few narrow, confluent ravines near the heart of the Mule Mountains, seven and one half miles north of the international boundary.  Within the Mule Mountains may be distinguished two topographic divisions, based upon geologic structure and roughly separated by a northwest-southeast line passing through Bisbee.  Northeast of this line, the mountains are sculpted from comparatively soft Mesozoic beds striking approximately with the trend of the range and dipping at moderate angles toward Sulphur Spring Valley.  The slopes of these hills are comparatively smooth, although the occurrence of a hard fossiliferous limestone in the middle of the group has occasioned a conspicuous and persistent cliff of erosion. 

Southwest of the divisional line, Paleozoic and older rocks prevail.  These are generally more resistant to erosion and more heterogeneous in character than the Mesozoic beds, and have a far more complicated structure.

The fundamental rocks of the Bisbee quadrangle are crystalline Pinal schists of Precambrian age, separated by a profound unconformity from the overlying Paleozoic beds.  The latter comprise a basal Cambrian quartzite 430 feet thick (Bolsa Quartzite), succeeded by over 4500 feet of limestone representing portions of Cambrian (Abrigo limestone), Devonian (Martin limestone and Mural limestone), Carboniferous (Escabrosa limestone and Naco limestone).

At the close of the Paleozoic period and during the Mesozoic, the rocks of the Bisbee area were deformed by faulting and folding and were cut by intrusions of granitic magma.  The principle mineralization of the district dates in the early Cretaceous. The region as a whole was elevated above sea level and subjected to erosion until the beginning of the Cretaceous period.  During the Cretaceous, the land again sank beneath the sea and over 4500 feet of sandstone, shales, and limestones were accumulated.  Subsequent elevation brought these sediments above sea level and exposed them to erosion.  During the Quaternary and probably during a part of the Tertiary, the higher parts of the Bisbee quadrangle have been undergoing erosion, their waste accumulating in the flat-floored valleys that surround the Mule Mountains. 

Prior to 1880 Bisbee was an unimportant lead camp.  The copper ore of the Copper Queen Mine was discovered early in this year.  This ore was free from sulfur and averaged 23% copper.  Ore minerals include: native copper, chalcopyrite, sphalerite, cuprite, azurite, malachite, brochantite, tenorite, and aurichalcite.  The Bisbee copper ores occur as large masses in the limestones and intrusive rocks.”

Maps of the Mule Mountains and Bisbee

Views of the Mule Mountains and Bisbee
Mule Mountains-Views of Historic Bisbee

reference articles
Geology and Ore Deposits of the Bisbee, Arizona Quadrangle   
       by F.L. Ransome, 1904, U.S.G.S. Professional Paper No.21
Geology of the Warren Mining District
       by Y.S Bonillas, J.B. Tenney, E.M Feuchre and Leon Feuchre, 1919, A.I.M.E. Trans.
Stoping in the Calumet and Arizona Mines
       by Philip D. Wilson, 1916, A.I.M.E. Trans. 

Intrusive Breccias Associated with Ore,  Warren (Bisbee) Mining District, Arizona
       by Donald G. Bryant, 1968, Bulletin of Economic Geologists
       vol. 63, no. 1, Jan.-Feb. 1968,  12 pages

Published references on the geology of the Mule Mountains and Bisbee 

Published references on Bisbee Minerals 

Published references on Bisbee mines and mining 
Stratigraphic Section Bisbee Area- from Jan Wilt

mine tour
Tour of the Bisbee Copper Queen Mine

Bisbee minerals

Cochise College Photos of Bisbee Minerals 

student presentations on the Mule Mountains and Bisbee
The Special Relationship between Azurite and Malachite- Jesse Smith  (Fall 2005)
The Worries of a Bisbee Copper Miner- Maria Ramos  (Spring 2006)

Phelps Dodge Corporation- Robert Hardy  (Fall 2007)
History of One of Bisbee's Families- Gina Thursby (Spring 2008)