Altered amygdaloidal porphyritic olivine basalt. Pseudomorphed euhedral phenocrysts of olivine and subhedral pyroxene are set in a dark grey fine-grained groundmass of pyroxene, olivine and feldspar. Olivine pseudomorphs contain dark oxide and carbonate. Amygdales have infillings of carbonate and silicate minerals, and many have reaction zones against groundmass in which the latter is lighter-coloured and coarser-grained.
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Corsi's classification:
Class 15. Porphyry; Species 1; ii. Italian porphyries