B. Silliman on the Mining Districts of Arizona. 301 
surfaces of crystalline quartz are also seen abundantly in all the 
“shuts” or closures of the vein. 
The hanging wall of the Moss lode is an ash-gray feldspathic 
porphyry, often intersected by thread veins of quartz and horn- 
stone, but barren of metallic sulphurets, and showing at the sur- 
face no clay wall or fluccan, separating it from the vien. The 
absence of this character of permanent and well defined lodes 
at the surface of the Moss ledge is in analogy with the character 
of many veins in Nevada, which, however, at moderate depths 
acquire this feature, as the Allen shaft shows to be the faet for 
the south or hanging wall of the Moss lode. The entire outcrop 
On the Moss lode has a burnt up, dried and hardened aspect, 
. 48 previously explained; and this character is shown now by 
' Very moderate explorations, to be quite superficial. 
The characteristic veinstone of the Moss lode is feldspar with 
veins of chert or hornstone, in which matrix occur veins o 
highly ferruginous quartz, sometimes almost an iron jasper of 
Various colors, sometimes compact and again cellular. The sur- 
faces of closure are drus , not separated from the gangue by 
any parting, but cutting it with a dip usually more highly in- 
clined than the dip of the vein itself. These intercalated or 
subordinate veins of quartz appear to maintain a course quite 
parallel with the main vein. ‘Too little work has however been 
4 limited sense, as far as can at present be seen, _ 
The rich specimens of free gold in quartz, of which over a ton 
The Moss lode has been opened by a shaft called Allen’s 
Shaft, sunk on the San Francisco claim, ten or twelve feet i 
front of the spot where the first lot ‘of rich ore was obtained, to 
@ depth, in Aug. 64, of 42 feet. This shaft was set to cut the 
hanging wall of the lode and pass through its entire thickness 
nh an estimated depth of about 100 feet. Where it cut the 
Southern edge of the lode ore was found from which an assay 
was obtained, showing $4,200 per ton of precious metals. 
I ordered this shaft cleaned up, to exhibit the nature of the 
section it has furnished of this side of the lode. The result was 
