| Text Description: |
Scoria from an eroded cinder cone. Fine grained, vesicular, holocrystalline, trachytic, seriate porphyritic, oxidized with a matrix of mesostasis, opaque, plagioclase and alteration. Plagioclase phenocrysts (small lath An38, large grain An55) are up to 1.25 mm, and most are small laths; some larger grains have oscillatory zoning or sieve textured zones. An altered phase, olivine?, up to 0.15 mm is present. Opaque phenocrysts are up to 0.3 mm. Mode: 77.9% matrix, 0.9% plagioclase, 0.5% opaque, 0.6% vesicles, 20.1% alteration |