1922] Vaughan: Geology of San Bernardino Mountains 355 



Furnace limestone.- — In a section on the northeast side of Horse- 

 thief Flat the Furnace limestone conformably overlies the Arrastre 

 quartzite with a dip of 35° to the southwest. In color this rock varies 

 from white to nearly black and in texture from coarsely crystalline, 

 individual crystals often being half an inch in diameter, to fine and 

 compact. An irregular mass sunken into granite nearly surrounds 

 Horsethief Flat and continues southeast to the Rose Mine with a strike 

 parallel to the general trend of the outcrop. It passes under the 

 Saragossa quartzite to the southwest, generally with a dip of 40° to 

 60° ; but in some places within the mass itself the dip is vertical. On 

 the northeast it is intruded by granite. In the vicinity of the Rose 

 Mine the limestone is penetrated by numerous small granitic dikes and 

 with these are associated ores of gold, copper, and lead. 



South and east of the Rose Mine the granite cuts the limestone into 

 numerous small isolated masses. A long tongue stretches eastward 

 and its eastern extremity lies in a trough of quartzose schists. 



Two miles up Antelope Creek from the Burns Canon road there 

 is a somewhat broken strip of limestone extending to the southeast. 

 Along the northern side tnere are small remnants of schist. Both 

 schist and limestone are intruded by granite and contact minerals 

 have been developed, particularly along fissures in the schist. Epidote 

 and garnet are the most abundant with occasionally some tremolite. 

 In some places these minerals are traversed by quartz veins. At the 

 contact with granite the limestone is entirely recrystallized, the average 

 size of the crystals being about two millimeters across, and is usually 

 white. 



A large isolated area of limestone is found east of Broom Flat, and 

 south of this, sunken into the granite, are many small areas which, for 

 the most part, have been altered to coarsely crystalline white marble. 



North and northwest of Sugarloaf Mountain there is a considerable 

 area of limestone. The eastern portion forms an anticline whose axis 

 is about a mile north of the peak and whose south limb dips 20°, pass- 

 ing beneath the Saragossa quartzite which forms the higher portion 

 of the ridge. The western half of this area is nearly surrounded by 

 intrusive granite and on the south side the latter has sent out many 

 large apophyses into the limestone. One point of interest in connec- 

 tion with this area of limestone is the occurrence of graphite in the 

 canon half a mile northeast of Sugarloaf Peak. It is present as a 

 stratum in the limestone and is usually impure, sometimes grading 

 imperceptibly into the limestone. It is of variable thickness, from one 



