In 1848 when Major Heintzelman opened headquarters in Tubac in southern Arizona and started operations at the old Cerro Colorado silver mine located about 25 miles northwest of there, Opeta Indians living in the vicinity frequently appeared at the store with large nuggets of native silver. No one new where the Indians found the rich ore, but the supply seemed to be unlimited.
When the Apache Indians started raiding the small ranches and mining camps in southern Arizona, the Opetas ceased making their prospecting trips to the south of the Tumacacori mission and Tubac and remained close to the post which was protected by soldiers. The mines were forced to close in the early sixties when the soldiers were withdrawn to fight in the civil war.
For a long period none of the silver nuggets were seen. Then one day in the early 80’s an old prospector walked into the saloon and gambling house of John Connors in Nogales and laid a large piece of native silver on the bar. Connors had been a miner for a number of years and had done some prospecting on his own account and immediately recognized the silver specimen as being valuable. The old prospector stated that he purchased the nugget from an old Opeta Indian living up on the Santa Cruz river near the little town of Tubac.
The Indian said the nugget had been picked up by him while hunting deer along Carrizo Creek south of the Tascosa mountains and that there was much more where that came from. This Indian farmer evidently did not think the nugget was valuable for it was purchased for a few dollars.
Connors purchased the specimen and agreed to grubstake the old prospector. Connors realizing the danger of sending an old man out alone induced him to take a younger man along. The two set out with their burros and were not heard from for several weeks. Then the younger man grew tired and returned alone to Nogales.
Weeks and months passed and then one day the old man appeared with his four burros loaded down with ore that was almost pure silver. The prospector told Connors that after the younger man left he prospected farther along Carrizo Creek toward the Mexican line and found the ground sprinkled with the large nuggets which had evidently eroded from an outcropping of kaolin.
The old man, elated over his sudden good fortune, spent his money freely at the bars and gambling tables and on the day set for the departure for the mine he failed to appear. A search party was started and the dead body of the prospector was found at the back of a warehouse owned by Connors. It had been a cold night and he had died from effects of drink and exposure.
Connors made several trips to the Carrizo Creek country but was unable to find any trace of the silver nuggets or the kaolin outcrop. The famous Planchas de Plata silver mine is located just across the border in Sonora and only a few miles south of the spot where the nuggets were reported to have been found by the old man.
It is a historical fact that at the Planchas de Plata many nuggets of native silver were found by the Spaniards. One nugget weighed 2700 pounds. Many others weighed from 25 to 250 pounds each. But the source of the four burro-loads of rich ore remains a secret shrouded in mystery.