Since the 1860s, gold placers in the Groom Creek Mining District near Prescott have drawn prospectors in search of fortunes.

These placers originated from quartz veins within pre-Cambrian schist intruded by granite, diorite and dikes of rhyolite porphyry.

Groom Creek is a southwestward flowing stream. Its headwaters in the Bradshaw Mountains (west of Walker in Yavapai County) around 6,500 feet down to 5,400 feet contain silver-gold bearing quartz veins. Its intermittent waters join the Hassayampa 5 miles south of Prescott.

By the turn of the century, it was estimated that over $100,000 of gold had been recovered from the district through placer mining.

A. J. Pickrell, a prominent geologist and mineralogist in Yavapai County, owned and operated assorted mining properties around Groom Creek with the intention of mining below the surface.

One of them was the Midnight Test Mine located on the northwest slope of Spruce Mountain at an elevation of 7,000 feet.

The mine began as shallow workings and a 400-foot shaft prior to 1906, with efforts made to mine a rich shoot of silver ore near the surface.

Primary transportation route was by the Senator Highway 5 miles south of Prescott and following a company mine road 2 miles southeast to the mine site.

Located along the strike of a dioritic intrusion around 2 miles long and up to half a mile wide, the quartz ore contains gold coated with iron and manganese oxides above the 600-foot level.

Known for its free-milling high-grade gold-bearing ore, the mine’s early production from 1900 to 1931 included $125,000 worth, of which $75,000 was gold and the remainder silver.

The National Gold Corp. further developed the Midnight Test Mine as one of its 20 contiguous mining claims including the Dixie and Saxon comprising 300 acres in the district during the 1930s.

As the primary property, the mine included a mill building, assay office, blacksmith shop and hoist shaft, with electricity powered by high tension power line through the Arizona Power Co. The electric hoist could service 1,000 feet of depth.

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A 200-ton mill working multiple shifts consisting of crushing, grinding and flotation produced up to 70 tons of concentrates per month. The mill included a Gibson amalgamator wherein 20% of the gold values were recovered as amalgam, up to 45% recovered in 4 Wilfley tables, and the remainder recovered through flotation.

Ore extraction involved air machines serviced by an Imperial Type 10 Ingersoll compressor and electric blasting on all levels.

Shrinkage or back stoping was employed due to the steep and dipping nature of the lenticular ore body, helping lower mining costs and reducing dilution of the ore to the caving of the walls. This method involved using broken ore and waste rock left in the stope as both a working base and wall support.

The mine consisted of workings including several thousand feet of drifts and raises, 14 stopes and a 600-foot-deep, two-compartment inclined timbered shaft. One compartment served as the ore elevator.

A headframe equipped with a two-ton automatic dump skip on wheels was used to hoist ore at a rate of 400 feet per minute. The other compartment was used for a manway along with housing for electric, water pump lines and ventilation.

The 600-foot-long Nevada Tunnel south of the shaft site was also projected to contain 2,500 tons of potential mill grade ore in a 700-foot- long vein above the tunnel as a continuation of the Midnight vein system.

Operations from 1902 through 1935 yielded 3,240 tons of ore comprised of 2,000 pounds of copper, 13,730 ounces of silver, 882 ounces of gold and 3,500 pounds of lead.

Ore reserves from blocks of ground samples showed potential for over 50,000 tons of possible ore reserves.

After having been promoted as a $2.5 million stock company in the mid-1930s, the mine closed due to lack of water caused by an arid winter and dried springs.

Lack of financial capital to sustain operations was another reason.

The mine subsequently went to receivership in the U.S. District Court and the property is currently owned by the National Forest.

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William Ascarza is an archivist, historian and author of seven books available for purchase online and at select bookstores. These include his latest, “In Search of Fortunes: A Look at the History of Arizona Mining,” available through M.T. Publishing Co. His other books are “Chiricahua Mountains: History and Nature,” “Southeastern Arizona Mining Towns,” “Zenith on the Horizon: An Encyclopedic Look at the Tucson Mountains from A to Z,” “Tucson Mountains,” “Arizona-Sonora Desert Museum” with Peggy Larson, and “Sentinel to the North: Exploring the Tortolita Mountains.” Email William Ascarza for a signed copy of his publications at AZMiningHistory@gmail.com.