362 The American Geologist. •'"°«' ^^^^ 
weathering of an orbicular gabbro, resembling that of 
Dehesa, California, described by Lawson* and by Kessler 
and Hamilton. t A few hundred yards to the west the 
orbicular rock gives place to a very coarse-grained gabbro, 
which grades into the noryte. 
Minerals Occurring in the Pockets. The minerals oc- 
curring in the pockets of the veins are : quartz, crystallized 
out on the sides, both of the clear and smoky varieties. 
These crystals are notable for the rather common develop- 
ment of rare cr\^stal faces. Hyalite and rose quartz are 
also sometimes found. Albite occurs with quartz, lining 
the pockets, and has a tabular habit of crystallization. Orth- 
oclase is usually found in pockets as individual crystals 
in the clay and is of the aventurine variety. It consists of 
microcline and albite in alternate bands. Muscovite, usually 
of a greenish tint, is found in plates of considerable size 
within the pockets, as scales or flakes making up a consid- 
erable part of the clay, and as minute scales included in 
other minerals. Lepidolite when found in pockets is usu- 
ally near the central part, and embedded in it are often 
found gem tourmalines and kunzite. This latter is often in 
fresh fragments and splinters, and also in fragments show- 
ing corrosion or decomposition. 
Crystals tend to grow to large size in these pockets. 
Although any one mineral may occur to the exclusion of 
the others, when several are found together, the orthoclase 
and kunzite are near the center, while the albite and lepi- 
dolite are near the walls. It is rare that kunzite and tour- 
maline occur in the same pocket. Even when in the same 
ledge, they are some distance apart. 
Vein Minerals Quartz, albite, muscovite and black 
tourmaline make up a good part of the paystreak. The 
mica often shows a crossing of plates as if of twinning but 
this is not shown by the optical figure. It is probably due 
to crushing or sliding action. The black tourmalines are 
also often intergrown and distorted, besides being broken. 
Lepidolite. varying in quality from the nearly pure lilac- 
* Bull. Dept. Geol. U. Cal. vol. Hi No. IT. Mat. 1904 The Orbicular 
Gabbro at Dehesa, San Diego. Co., Cal., by A. C. Lawbon. 
t The Orbicular Gabbro of Dehesa, Cal., bv H. H. Kb^slkr and W. R. 
HAMILTON, The Ambrican Gkolooist. Sept., 1904. 
