A Geoscience Digital Image Library

TitleThin section of trachyte porphyry (bostonite)
DescriptionThis is a photo of the plain polarized thin section of trachyte porphyry. Prominent phenocrysts are blocky to subrounded sodic orthoclse, turbid and zoned, some are glomeroporphyritic. The matrix consists predominantly of equigranular tablets of zoned hematitic orthoclase, euhedral and in subparallel (trachytoid) arrangement. A few original mafic grains (pyrozene?) now consist of cerisite, calcite, hematite, magnetite and sphene. Abundant accessory magnetite has been altered to hematite. Interstitial accessories are widespread: anhedral quartz, amall zircon euhdra, sericite flakes and grains of calcite. Veinlets of hematite cut the rock.
ChronostratigraphyPost Ordovician
LocationUSA ▹ New York ▹ Essex. Near Essex.
PhotographerDarla Sondrol. 2002-04-02.
CollectionWard’s Collection of Classic North American Rocks #15.
Key wordstrachyte, porphyry, bostonite, New York
Tech details969 KB. Thin section. Nikon FDX-35.
GeoDIL number2557