Abstract

The yellow substance coating the rim rocks of Paradox Valley was probably used as a pigment by Native Americans before the settlers arrived. Soon after the Ute Indians were removed from western Colorado in 1881, prospectors were intrigued by the yellow material on the rim rocks especially along Roc Creek and adjacent areas. Assayers were unable to determine the elements in this substance. In 1898, a sample was sent to a French chemist in Denver, Colorado, who found it contained uranium and was valuable. In June of that year, ten tons of high grade ore (21.5 percent uranium oxide) from Roc Creek was sent to Denver and on to France. In that same year, Marie and Pierre Curie, working with pitchblende from Bohemia, discovered that all uranium ores contained a new element, radium. The next year, two French chemists determined the analysis of the Colorado material and named a new mineral, carnotite, a potassium uranium vanadate after the French scientist, Adolphe Carnot.

About 1909, a process to recover radium from carnotite was developed in the United States. By 1911, hundreds of claims had been staked in the Paradox Valley and adjacent areas. Prospectors recognized the most productive horizon was the upper sandstone rim in the lower McElmo Formation and noted the association with organic material, especially ‘fossil trees’. Today, this unit is known as the Salt Wash Member of the Morrison Formation.

One gram of radium could be extracted from 200–300 tons of ore containing two percent, or greater, uranium oxide. For ten years (1913–1922) the carnotite deposits of southwestern Colorado and southeastern Utah became the principal world source of radium. Prices ranged from $70,000 to $180,000 per gram. The Standard Chemical Company was the principal operator in the region. The boom ended in 1923 when lower cost pitchblende ores from the Belgium Congo, now Democratic Republic of the Congo, took over the market and forced most United States mines to close.

Between 1910 and 1923, some 202 grams of radium, valued at $20 million had been produced. Vanadium and uranium were recovered as by-products. Contrary to folklore, Madame Curie never visited the carnotite region.