The missionaries had a second goal when they discovered silver in the area in 1766. Quickly, they put the Indians to work mining the silver in several mines throughout the area.
The Opata Indians preferred working in one particular mine more than the others and the missionaries allowed this, as the mine was highly profitable. At the back of this mine was a giant room where all of the silver was stored in a pile in the center of the room.
Despite their best efforts at converting the Indians, the Opata utilized the big room, piled with silver, during the night to perform their old pagan religious rites. However, they must have absorbed some of the preachings because when they saw a Mayo Indian Princess traveling in the desert, they were convinced that she was the next Virgin Mary.
Kidnapping her, they took her to the big room piled with silver and told her that she would marry their chief in order to produce a child savior. The princess refused, saying that she would rather die. The Indians retaliated by deciding that if she would not marry their chief, then they would sacrifice her for their gods.
One Sunday when the Indians had the day off, they tied the princess to the mound of silver in the center of the room. The chief gave her one last chance to marry him or die, and she choose death. The chief then cut her hands, rubbing poison into her blood, and telling her when the sun touched the wounds, she would die. As a small ray of sunlight beamed through a hole in the center of the room, the Indians began to dance and sing around her.
When one of the missionaries heard the commotion coming from the mine he went to investigate and found the dead princess still tied to the silver and the Indians dancing around her. Appalled that their preachings had been so violated, the missionaries sealed the mine entrance shut, leaving the princess and all of the silver inside.
According to the legend, both the silver and her skeletal remains still lie hidden somewhere near the Tumacacori Mission. Old Spanish records place the Opata Mine halfway between the Guadalupe Mine and the Pure Conception Mine, just waiting to be found.
The Tumacacori Mission and the surrounding area is now a national park.