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Looking Back to 1955: Uranium discovery on Twisselman ranch causes mining fever 

Looking Back Paso Robles

This look back at Paso Robles history comes from local newspapers in the Paso Robles Area Historical Society collection. News for this column is selected with the assistance of the society’s Vice President Nancy Tweedie and Research Director Jan Cannon. Newspaper photography by GiGi Green.

Excerpts from Sunday, April 24, 1955 Sunday Review

Confirmation of a uranium strike fifty miles east of Paso Robles and north of the Carissa Plains was spreading a mild case of mining fever throughout the area today, as discoverers of the lode moved “head off an hysterical stampede of amateur prospectors.”

Apparently the deposit is on an extensive tract of land on the Theodore Twisselman ranch. The initial discovery three months ago was made by Twisselman and Otto Van Horn, Paso Robles realtor. Since that time survey work has been conducted by Maurice DuBost and Donald Thorpe, copartners in the firm D&T Enterprises, who have gone over the land with a scintillator and a Geiger counter.

Paso Robles History uranium mineLand leased

This week, following the unearthing of commercial-grade ore by bulldozer operations, the tract was leased to the St. Anthony Oil Company, of Los Angeles for intensive development. Lessors are the Twisselman family — Ernest Still and family, and Jacob Martins, John Gallagher, Maurice DuBost and Otto Van Horn.

The lessors stressed yesterday that the strike is located on private land and there is no open land within miles of the location.

DuBost said that the newly formed firm hoped to avoid a “futile stampede for claims — all of the land is privately owned. But the rush for claims, recently by Bakersfield prospectors, following discovery of the Miracle Mine lode in the Kern River Canyon, stampeded thousands of head of cattle and destroyed miles of ranch fencing.

Ted Twisselman and Otto Van Horn decided 90 days ago that some “diggings” on the Twisselman property “might be worth investigating,” DuBost said yesterday. Thorpe and DuBost were asked to survey the area with a Geiger counter and Scintillator, and located “a number of hot spots.”

Above minimum standards

“The ore we’ve tested is higher than the minimum set for commercial grade,” DuBost said. (Commercial must test ten one-hundredths of one per cent).

The technicians admitted that the ore “looks good on the surface, but it is impossible to say what is underneath. It could have come up to the surface, carried by subterranean waters,” Thorpe speculated, “which means that there is a lot more beneath the surface. “Or,” he added, “the present deposit may have leaked down from the surface during eons of time, and that case the deposit probably would not be too large.


“I would classify the strike as minor, in terms of the Colorado findings,” he added, “but the term ‘minor’ is relative. I think there is good chance that this deposit may produce a substantial amount of high quality ore. However, no one will know the answer until much extensive investigations have been completed.”

“The ore we’ve found is lying in sedimentary beds and covers a very large area, but is not deposited uniformly.”

“Approach to the recovery of the ore will be dependent entirely on its concentration. If a heavy deposit is found near the surface, it may be scooped up by power equipment in a pit operation. If it is impossible to locate a heavy deposit of this type, then the logical procedure is to drill holes and sample the ores, and formulate a topographical map which will indicate where the main beds lie.”

“If the company decides that the uranium is in a true vein, that is, associated with a fault, they will probably drop a shaft down to it and follow the deposit.”

Dozer cuts

At the present time bulldozer cuts twenty to twenty-five feet deep, made at points indicated by DuBost and Thorpe, have revealed enough ore to interest an Atomic Energy Commission geologist who reported that the ore has been classified as Autinite, a calcium-uranium phosphate. The ore has a characteristically brilliant chartreuse color under ultra-violet light.

Editorial note

The Western Mining History website places the Twisselman uranium prospect in Kern County, near Lost Hills. Prospects are locations that are potential sites or mineral deposits. Another website, Diggings, lists 37 uranium prospects and one mine with San Luis Obispo locations, some producing other ores as well. Locally, in North County, Diggings lists:

  • Nine prospects near Creston, two with gold and uranium and the rest with uranium.
  • Three uranium prospects near Santa Margarita.
  • Pine Mountain Mine near Templeton CA (mercury, uranium, gold and silver). Owned by the Hearst Corporation the mine was discovered in 1875 and is now located within the Los Padres National Forest. Western Mining History lists it as a “past producer.”

Read previous Looking Back articles

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About the author: Reporter Jackie Iddings

Jackie Iddings is a contributing reporter and photographer for the Paso Robles Daily News.