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World famous as a source of gem and lithium minerals, the Pala pegmatite district encompasses more than 400 pegmatite dikes in an area of some 30 square kilometers (13 square miles). The heart of the area covers some 15 square kilometers (6 square miles).
Most of the district is underlain by intrusive rocks of
the Cretaceous period which are part of the complex Southern California
batholith. The batholith is formed
of many separate units and ranges in composition from gabbro to granite.
The pegmatites occur mainly in the gabbro rock and were emplaced along
well-developed fractures. They range
in thickness from small stringers to dikes more than 30 meters (100 feet) thick.
These pegmatites are very coarse-grained, igneous rocks, irregular in
texture and with some extremely large crystals.
Most of the pegmatites are well exposed despite the thick chaparral
cover, and form low knobs and rib-like protuberances on the hillsides.
Over 86 different minerals have been found in the
pegmatites, including tourmaline, spodumene, beryl, quartz, albite, biotite,
garnet lepidolite, and kunzite.
largely inactive today, there has been considerable mining in the area.
R. H. and L. A. Wright, 1951. Gem
and Lithium-bearing Pegmatites of the Pala District, San Diego County, Calif.
Calif. Div. of Mines Spe. Rep. No. 7-A, 72 pp.
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