Porphyrtic trachyte. Abundant feldspar phenocrysts up to 15mm showing complex twinning, concentric zoning of inclusions and a tendency to cluster. Sparse microphenocrysts of amphibole substantially altered to rusty brown mineral (also occurs in the white feldspars). Possible rare quartz phenocrysts. Groundmass of milky-white and pale grey feldspars showing tendency to fluidal structure round phenocrysts. Occasional angular (?cognate) xenoliths of fine-grained equigranular rock consisting of feldspar and altered amphibol;e.
Comments:
This has not been identified as coming from Egypt.