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Unnamed Corundum occurrences, San Jacinto Mts, Riverside Co., California, USA

Corundum
Unnamed Corundum occurrences, San Jacinto Mts, Riverside Co., California, USA

Photo: 2003 SLR
Corundum occurrences located in sec. 5, T4S, R1E, SBM, near the summit of the mountains.

Geology:
The deposits are located along the contact of granodiorite/quartz diorite host rock and metamorphosed marine sediments. Several small biotite schist bodies at the contact zone contain random sprays and clusters of corundum crystals, up to 2 feet long and 3 inches in diameter. The crystals are included with biotite so severely that in some crystals there is partial replacement. Much of the schist has been decomposed to an iron-stained micaceous clay, which contains inclusions of quartz and feldspar. Quartz veins with feldspar and garnet occur nearby.

History:
According Fred Rynerson, the first report of corundum crystals from the area was made around 1924, by an unnamed woman about 60 years old that had brought a dozen crystals to Ward's Lapidary shop in San Diego for appraisal. The largest crystal was said to have measured approximately 2 inches long, and 3/4 inch at the base, tapering to 1/2 inch at the top. The woman reported that the crystals were scattered over the side of a small hill behind her house. Four years later, Rynerson searched several collections in Riverside County for the source of these crystals, but was unable to find any information about the deposit.

In 1939, large crystals of corundum embedded in mica schist were submitted to the Department of Geology at UCLA, by Mr. B. G. Funk of Los Angeles. These specimens showed sapphire-blue cores, with a progressively zoned gray colored outer rim included with micaceous material. The area was visited around 1940 by Joseph Murdoch and Robert W. Webb, who reported corundum crystals having been found as float in many parts of the San Jacinto Mountains. Several decades later, Mark Rogers reported that several crystals up to 12 inches long, both loose and in schist matrix, had been collected from the area in the late 1940's by a married couple of Asian decent.

In 1980, brothers Ken and Dana Gochenour visited the area several times and eventually discovered a small outcrop of corundum-bearing schist that contained crystals up to 4 inches in length. In 1999, the Gochenours reported finding the remains of an old working that contained a dark biotite schist with broken crystals up to 12 inches long and an inch in diameter. This schist had some crystals that were up to 7 inches long in situ. Several other locations were later discovered while prospecting along the surface, and over 150 pounds of large corundum crystal segments were said to have been collected from the area.

Mindat Articles

Corundum Crystals from the San Jacinto Mountains by K. L. Gochenour 2000 by Scott L. Ritchie


Mineral List

'Albite-Anorthite Series'
'Biotite'
Calcite
'Clay'
Corundum
var: Sapphire ?
Diopside
'Feldspar Group'
Grossular
'Hornblende'
'Mica Group'
Muscovite
Orthoclase
'Pyroxene Group'
Quartz
Wollastonite


16 entries listed. 8 valid minerals.

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References

Gochenour, K.L. (2000), The Rediscovery of Corundum Crystals from the San Jacinto Mountains, Riverside County, California Lithosphere bulletin, May/June. Fallbrook Gem and Mineral Society, Inc., Fallbrook, California.

Murdoch, J., and Webb, R. W. 1942. Notes of Some Minerals from Southern California, III: Corundum and Associated Minerals near Banning, San Jacinto Mountains, California. The American Mineralogist. 27(4): 328-329.

Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 161.

Rynerson, F.J. (1967) Exploring and Mining Gems & Gold in the West; Ch. 23: 151: Naturegraph Publishers, Inc., Happy Camp, California.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 143.

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