Veinlets of a vitreous nonfibrous transparent mineral were observed on a specimen of bedded euhedral borax and clay from the Jenifer mine by Siegfried Muessig, U. S. Geological Survey. The vitreous mineral, first recognized after the enclosing vitreous borax had dehydrated to white tincalconite, was subsequently identified as strontium-bearing ulexite by chemical analysis and verified as ulexite by x-ray examination. The ulexite veins, which occur in a zone up to 10 mm. wide, are from less than 1 mm. to 4 or 5 mm. wide and irregularly separated by borax—now altered on exposed surfaces to tincalconite. Clay and disseminated realgar are associated with both borax and the ulexite.

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