COPPER DEPOSITS OF BISBEE. ARIZ. 
By F. L. Ransome. 
INTRODUCTION. 
During the autumn and winter of 1002 a detailed geological inves- 
tigation was made of the Bisbee quadrangle, embracing the greater 
part of the Mule Mountains, by F. L. Ransome, assisted by J. Morgan 
Clements and Alfred M. Rock. The geology of the quadrangle was 
mapped on a scale of approximately 1 mile to the inch, Avhile an area 
of 8 square miles in the immediate vicinity of the principal mines was 
mapped geologically on a scale of 1,000 feet to the inch. The material 
gathered during the progress of the field work will shortly be embodied 
in a full report upon the geology and ore deposits of the district. In 
the meantime the following brief sketch includes only such salient 
results of the unfinished investigation as seem least likely to be modi- 
fied by further study. 
GEOGRAPHY. 
The Warren mining district, in which occur the ore bodies that 
have given Bisbee its prominence, lies in the central part of the Mule 
Mountains, a generally northwest-southeast range, some 30 miles in 
length, extending from the old mining town of Tombstone down to 
the Mexican border. In the vicinity of Bisbee the range attains an 
elevation of 7,400 feet and has a width of about 12 miles; but in the 
neighborhood of Tombstone and near the international boundary line 
it is represented by clusters of comparatively low hills. On the south- 
west the Mule Mountains are separated by the broad valley of the San 
Pedro from the Huachuca Mountains, and on the northeast by the 
similar wide expanse of Sulphur Spring Valley from the Swisshelm 
and Chiricahua ranges. On the north a few low hills just southeast 
of Tombstone connect the Mule Mountains with the Dragoon Range. 
The town of Bisbee, with a population estimated at about t>,000, is 
crowded into a few narrow confluent ravines in the heart of the range. 
It is connected by the El Paso and Southwestern Railroad with El 
Paso, with Benson on the main line of the Southern Pacific Railway, 
and with Douglas and Naco on the international boundary. 
GENERAL GEOLOGY. 
The oldest rocks in the Mule Mountains are fine-grained sericite- 
schists, derived from ancient sediments. These were probably origi- 
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