MONTEZUMA KANGE. 759 



It is worthy of mention here that the ore of the Montezuma Mine is 

 of a peculiar character, consisting of a highly oxidized product derived from 

 the decomposition of some antimonial lead mineral, probably jamesonite, 

 as bright unaltered fragments belonging to the latter species have been 

 found in the mine. The decomposed product, from its physical and chemi- 

 cal properties, has been identified as bindheimite, agreeing closely with the 

 variety found in Cornwall, where it is also associated with jamesonite. It 

 has a fibrous structure, a yellow or yellowish-brown color, and gives a faint 

 yellow streak. Prof William G. Mixter, of the Sheffield Scientific School 

 of Yale College, analyzed the mineral, and obtained the following compo- 

 sition : 



Antimonic acid . . 51.94 



Oxide of lead 40.89 



Silver 0.33 



Ferric oxide . . • 60 



Insoluble residue ^ .« 1.66 



Water 4.58 



100.00 



Volcanic eegion south op Trinity Peak.^ — As already mentioned, 

 the southern end of the range, below the Trinity Peak Archaean region, con- 

 sists mainly of volcanic rocks, and of these rhyolites and basalts form all 

 the more prominent portions. Indeed, so far as known, with the exception 

 of an outburst of propylite at the' extreme southern end and a few doubtful 

 rocks of obscure exposures, no other Tertiary eruptions were recognized. 



Valley Canon, next south of Trinity Canon, penetrates a wide area of 

 low rhyolitic hills, having a great diversity of color and outline. About 3 

 miles up the canon, there occurs a heavy outburst of rhyolite, of the pearlitic 

 variety, more recent than the main crystalline fields, and forming quite reg- 

 ular hexagonal columns. In the gra}^, glassy base are observed a quantity 

 of cracked sanidin crystals, frequently one-fourth of an inch in length, con- 

 siderable dark biotite, and some hornblende. Free quartz would appear to 



* lu part from notes furuished by Mr. Clarence King. 



