MINES OF GOLD HILL. 
301 
(See PL II, in pocket.) The southeasterly dip of the contact, near the bend in the 
latter between the Conundrum and Abe Lincoln mines, is thus probably rather under 
40°. In both the Midget and Conundrum mines the gneiss, sometimes for a hundred 
feet or more from the volcanic breccia, is shattered to fragments, which often average 
only 2 or 3 inches in diameter. This shattering is very noticeable along both sides of 
the Conundrum lode, and it is usually impossible to determine closely where the shat¬ 
tered gneiss ends and the volcanic breccia begins. The fragments of gneiss are partly 
separated by interstices as if the liner material had been in part removed. The frag¬ 
ments are in some cases only slightly coherent; in others they are coated and cemented 
by crystalline envelopes of purple flfiorite. The shattering evidently antedated the 
intrusion of the basaltic dike, as the latter is not brecciated. 
The breccia in the Midget and Moon-Anchor mines is more varied in texture and 
composition than is common in so small an area. It usually contains abundant frag¬ 
ments of phonolite, schist, granite, and gneiss held together in a matrix containing 
many minute particles of pink feldspar, evidently derived from the granite and gneiss 
of the vicinity. This variety of the breccia may be well seen in the dump of the Ben 
Hur shaft, south of the Midget. Another variety occurs along the general line of the 
Midget lode, particularly between level 6 and the surface, where it may be seen in 
various pits between the Moon-Anchor and Midget shafts. This is a line-grained 
altered tuff, which underground somewhat resembles decomposed basalt, and is 
characterized by a reddish or purplish tint. The clastic structure of this material is 
sometimes plain, sometimes obscure, and in the latter case the rock is often called 
basalt by the miners. 
The breccia in the'Midget and Moon-Anchor mines has undergone local shat¬ 
tering similar to that already described in the gneiss near the Conundrum lode. In 
the Midget this shattered rock occurs in the vicinity of the shaft on levels 7 and 8, 
passing into brecciated gneiss on levels 9 and 10. The rock is a loosely coherent, 
porous mass of angular fragments, showing considerable pyrit.ic mineralization. 
' No ore occurs in this material, and lodes as they enter it from the solid breccia are 
lost. Similar shattered breccia occurs on levels 7, 8, and 9 of the Moon-Anchor 
mine just northwest of the shaft, the material looking as if it had been passed 
through a rock crusher and dumped into an old stope. The fragments are in part 
loose, in part cemented at points of contact by pyrite and quartz. This material 
passes peripherally into breccia traversed by countless fractures belonging to 
sheeted zones running in various directions through the rock. This fissured rock in 
turn passes gradually into breccia showing only the usual amount of jointing. 
Both gneiss and breccia are cut by several irregular dikes of phonolite, which 
are also locally shattered, though usually less so than the breccia. These dikes 
are often indistinct and difficult to trace in the breccia, particularly in the shat¬ 
tered portions. 
The Conundrum basalt dike strikes on the whole a little west of north and dips 
about 70° E. It is rather curved and irregular and ranges in width from a frac¬ 
tion of an inch up to 3 feet. It is usually mineralized, constituting ore, or is soft 
and decomposed. 
13001—No. 54—06-21 
