Be content was determined by spectrographic methods in more than 180 glassy or partly glassy silicic volcanic rocks from the Cordilleran region of the U. S. Be contents range from 0 to 20 ppm. Distribution is approximately log-normal over most of the range. The median is about 3.6 ppm, comparable with but slightly less than that found for granitic rocks. The distribution of Be in these rocks is closely related to the distribution of F; similar relations are apparent in ore deposits of several types. The regional distribution of Be is non-random; high contents are concentrated in a region trending southwestward from central Montana into northeastern Nevada; another belt, with a generally northerly trend, lies in western New Mexico and central Colorado. Some high analyses come from the Big Bend region of Texas. This distribution may be especially significant in prospecting for other Be deposits in altered tuffs, such as that recently found at Spors Mountain, Utah.

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