Abstract
Three specimens of capsular silica have been collected by the writer from the Quaternary formations of Brazos County, Texas. Clastic fragments of petrified wood are very common in these formations, and much opal and botryoidal chalcedony is found as veins and incrustations with the wood. The Tertiary and Quaternary formations of the county are exceptionally rich in precipitated silica which occurs as quartz, chalcedony, and opal. These three minerals are found in the forms of petrified wood, veins, rock cement, silica-limonite hardpan, case-hardening, sep-taria, and melikaria.1
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