"Thorium deposits were discovered in the Powderhorn district in 1949. This district has long been known for its occurrences of alkalic igneous rocks, of which the best known is the Iron Hill complex (Larsen, 1942). Some of these alkalic rocks contain titanium, barium, strontium, rare earths, thorium, and niobium in greater percentages than those of most igneous rocks. A study of the thorium deposits was undertaken to obtain more information on the geologic relation of minor elements, particularly rare earths, and thorium, to alkalic igneous rocks, and to evaluate the economic significance of the Thorium deposits."