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Trask mine, San Diego Mine (K. C. Naylor mine), Gem Hill, Mesa Grande District, San Diego Co., California, USA

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The Trask mine is located just south of the center of the SE4SW4 Sec. 17, T11S, R2E, SBM, approximately 2.75 miles (4.42km) northwest of Mesa Grande, situated high on the eastern slope of Gem Hill, at an elevation of approximately 3822' AMSL.

A southerly extension of the north-trending Himalaya pegmatite dike system. The dike dips approximately 35 degrees west, and ranges in thickness from 16 to 25 inches. Pocket pegmatite is widespread in the central part of the dike which is composed mainly of coarse-grained quartz-euhedral perthite pegmatite. The pocket zone forms thin lenticular masses.

The Trask mine was a short-lived underground gem mining operation, active from 1909 to 1912. The property was a small "L" shaped land area that contained approximately 122 feet of land along the strike of the main Himalaya dike - located between the Himalaya Mining Company's boundary to the north, and the San Diego Tourmaline Mining Company's boundary to the south (form. Lewis Ranch).

The primary development consisted of a single cut and inclined shaft approximately 100 feet long and 65 feet deep, following the dip of the main Himalaya dike, from which stopes were developed north and southward. Most of work was performed by Frank Trask, together with Fred Rynerson and Gail Lewis, under a joint venture with Nickelson and Harsch of the Mesa Grande Consolidated Gold and Gem Mining Company.

Rynerson described Trask finding tourmaline crystals in the dirt as he dug the main cut, which progressed into a continuous series of pockets while following the vein downward. Production consisted of a large amount of pink tourmaline nodules and pencils, as well as some stibiotantalite crystals.

The mine was later sold to K. C. Naylor of the San Diego Tourmaline Mining Company, and the land was eventually consolidated into the San Diego mine property boundaries.

Mineral List

8 entries listed. 4 valid minerals.

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Weber, F. H. (1963a), Geology and mineral resources of San Diego County, California. California Division of Mines and Geology, County Report 3: 113.

Rynerson, F. J. (1967), Exploring and mining for Gems and Gold in the West. Happy Camp, California: Naturegraph Publishers, Inc., pages 12, 26, 38-41, b&w photographs.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 448 (map 13-1).

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