Grand Reef Mine, Laurel Canyon, Grand Reef Mountain, Klondyke, Aravaipa Mining District, Graham County, Arizona, USAi

Regional Level Types
Grand Reef Mine	Mine (Inactive)
Laurel Canyon	Canyon
Grand Reef Mountain	Mountain
Klondyke	- not defined -
Aravaipa Mining District	Mining District
Graham County	County
Arizona	State
USA	Country

A former underground Pb-Cu-Ag-Zn-Au-Mo-V-Baryte-Fluorspar-Silica mine located in the E½ sec. 29, T6S, R20E (Cobre Grande Mountain 7.5 minute topo map), in Laurel Canyon, 4.6 miles SSE of Aravaipa, and about 4 road miles NE of Klondyke. The Aravaipa shaft is 1½ miles farther north. Discovered 1n 1890. Owned by the American Zinc, Lead, and Smelting Co. of St. Louis, MO (1950). First produced 1915. Also known as / designated: George H. Botts, John W. Mackay, and Patented claims MS 1760.

Mineralization is a tabular ore body hosted in Pinal Schist and limestone. The ore zone is 36.58 meters long, 9.14 meters wide, with a depth to bottom of 234.7 meters, striking N12W and dipping 85W. Associated rock units are the Horse Mountain volcanics and the Goodwin Canyon Quartz Monzonite. Ore control was breccia in the Grand Reef Fault within rhyolite porphyry which is intruded by granite. Alteration is silicification.

Area structures include the Grand Reef Fault and block faulting trending NNW. Regional trends: minor Pre-Cretaceous E- and NE

The Grand Reef lode occurs within iron-stained, silicified breccia cemented with quartz and other vein minerals. In Laurel Canyon the breccia forms a reef more than 100 feet wide and over 200 feet high. It strikes approximately N.12ºW. and dips from 70º. to almost vertical. Southward it separates into smaller branches such as the Silver Cable and Dog Water lodes (See the Silver Cable and Dog Water Mines). Below adit level the ore body was 40-50 feet long, 10-15 feet wide. Lead and zinc sulfides and oxides occur in fissure veins and replacement bodies in rhyolite and intensely brecciated limestone. The veins are in low-angle falut zones.

The reef occurs within rhyolite porphyry, which is a short distance father east, and is intruded by granite of the main batholith. In places diabase appears between the granite and rhyolite. A narrow belt of schist has been reported along the western border of the granite.

The main Grand Reef stope exhibits numerous fractures striking N.60ºE. and dipping about 80ºSE. A main break along its axis strikes slightly east of north and dips steeply east to vertically and steeply west downward to the adit level; associated with it is considerable iron stain as well as white clay alteration. Along the west wall of the stope is a vertical break trending approximately north. The southeast apex of the stope is along a fissure that strikes NE and dips 75ºSE; it is marked by considerable iron oxide, local copper stain, and white clay alteration.

Where exposed, the rhyolite in the hanging wall shows alteration to white clay minerals, intense for more than 50 feet and notable for 1,000 feet west of the Grand Reef stopes. Strong alteration of similar character appears on the west side of the Dog Water lode.

The outcrop over the Grand Reef stopes is marked by a grayish-brown color, in contrast to the darker brown tint that prevails immediately north of the ore shoot. Much of the reef south of Laurel Canyon is concealed by Tertiary gravels.

The principal known ore shoot, as stoped on and above the adit level, was 120 feet long and from 15 to more than 30 feet wide. Ore was found below these stopes, to the bottom of the winze. Smaller ore shoots were opened 10 feet west of the main shoot; 600 feet farther north, both on the ridge and in the adit; and south of the winze on the 200 level.

The ore is mainly breccia cemented with fine-grained quartz containing specks of fluorite and flakes of chlorite. Quartz also occurs as irregular bands of light grey chert, as drusy veinlets, and as white to pink vitreous masses. The most abundant sulphide is galena. It forms irregular fragments and bands and commonly includes tiny blebs of acanthite. A little sphalerite and chalcopyrite are assocated with the galena, but pyrite is scarce.

The ore is partly oxidized, and a mass of oxidized ore was reported to occur on te 300 level. Limonite, although not plentiful stains the outcrop.

This mine has a total more than 4,000 feet (1219.2 meters) of workings. The haulage level is an adit about 1,400 feet long, run northward beneath the main stopes. A winze extending 300 feet (91.44 meters) below the adit under the stopes area, has three levels of drifts at 100-foot intervals. Between 1890-1900 the mine was opened to a depth of 300 feet. The haulage level in 1950 was the 1400 foot long adit.

According to Ross 1,389 tons of shipping ore came from the Grand Reef mine during 1915-20 and of the concentrates, 2,613 tons were from te Grand Reef. Production years were 1907-1908, 1915-1920, and 1929-1931. Ranked as second producer of lead in 1931. Except during 191, the Grand Reef Mine yielded most of the output of the district during 1915-1920, 1929-31, and 1937-41. Assays (1915-1920): 2.83% Cu, 40.9% Pb, 1.4% Zn, 0.01 oz/ton Au, 20 oz/ton Ag, 2.4% Fe.

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Link to USGS MRDS:	10039486

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References