364 
• The American Geologist. ''^^^- ^^^^ 
SiO= 
LiO' .23 
Al^C^ 
35.55 Na^'O .19 
Fe=0» 
.21 K^O .03 
MnO 
.26 H^O (107°) 6.63 
CaO 
1.02 H^O (above 107°) 12.25 
MgO 
. 19 TiO== none 
100.18 
This analysis agrees closely with the formula H*ArSi* 
Q9_j_jj'0. It will be noticed that no boron was found 
in this clay. 
A small amount of a white finely granulated mineral 
has also been found in the pockets. The microscope 
shows it to be composed almost wholly of fresh angular 
fragments of feldspar, which contains manganese. 
T/ie J^ I neon District. Eastward toward Rincon the 
vein structure again becomes evident on the north side of 
the valley, and at the base of the Palomares mountains 
above Rincon another mineralized area occurs. But here 
the country rock is mainly a decomposed granite, with the 
veins standing out prominently. These have the usual 
structure but the association of minerals is somewhat dif- 
ferent. Crystals of quartz, orthoclase and beryl are the 
pocket contents. Black tourmaline, patches of massive 
almandine and large beryls are common in the hard peg- 
matitic material. Greenish muscovite is also very notice- 
able in patches several inches in extent. The pegmatyte 
in some places has a very coarse structure in which the 
individual quartz and orthoclase crystals are several inches 
in extent, as shown in plate xxv. 
Only two veins have been prospected enough to show 
the occurrence of minerals. From the lower of these, over 
$2,000 worth of gem beryls have been taken with the re- 
moval of hardly a hundred cubic yards of material. The 
beryls occur in clay in pockets usually not over eight inches 
in diameter, in the central portion of the ledge. In the 
upper vein are found many pockets filled with a red clay 
composed of mica and iron-stained kaolin. Many small 
beryls occur in this, but are uniformly of a milky hue. 
Smoky quartz, often intergrown with mica (plate xxiii, fig. 
2), and orthoclase crystals (plate xxvi, fig i), several inches 
in diameter are found in the larger pockets. The latter are 
