Day #109 Deskcrop: Sillimanite Schist, Tracy Hill Road

Concluding the Barrovian metamorphic index minerals theme I began last week (as a series of clues to WoGE #198), today’s deskcrop is a sillimanite zone muscovite-rich schist from Dutchess County, New York. There is no sillimanite visible in hand sample (like most sillimanite +/- K-feldspar-zone metapelites I’ve known, but not all), though there are some bodacious garnets hidden in that sea of muscovite. The Barrovian-sequence metapelites from Dutchess County were the topic of a two-week metamorphic petrology lab in my undergrad days at Colgate University, and names like Tracy Hill and Still Road bring back memories of that lab with a fondness that undoubtedly grows with the passage of time.

Sillimanite Schist, Tracy Hill Road

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