| Text Description: |
Float boulder of silicic material at Site 1 in the Boyden Hills. Fine-grained, vesicular, hypocrystalline, locally pilotaxitic, porphyritic to glomeroporphyritic with a matrix of cryptocrystalline material, opaque, feldspar, small amount of brown glass in glomeroporphyritic clot, and minor colorless glass patches. Plagioclase phenocrysts (An39 - An62) are up to 2.38 mm and both oscillatory and normal zoning are common; a few grains have resorption embayments that were later overgrown; there are occasional poikilitic orthopyroxene inclusions and some brown glass melt inclusions. Orthopyroxene phenocrysts are up to 1.3 mm, display intense pleochroism, large opaque inclusions, and some have brownish coating. Amphibole phenocrysts are up to 0.8 mm display red-brown or red-green pleochroism and have opaque coronas. Opaque phenocrysts are up to 0.48 mm. |