The company said the closure was necessitated by weak volcanic rock above the ore deposit which allowed water to flow into the mine.

FORBES: The perils of mining

What was decades ago a lump of rock can be transformed into an economic ore by new technology.

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At Goliad the uranium ore is located just 400 feet deep within the same rock as a groundwater reservoir that ranchers tap for drinking water, both for themselves and their livestock.

FORBES: Energy's Latest Battleground: Fracking For Uranium

The ore is pulverized in a crusher that can smash 300 tons of rock per hour.

FORBES: The Treasure of the Sierra Madre

Rock-breakers work with geologists and surveyors to make sure that only profitable grades of ore are mined.

ECONOMIST: South African gold mining