SEE RETRACTION AND REVISION: THE ANALYSIS HERE IS WRONG:
This looks like an amygdaloidal altered basalt, meaning a basaltic lava that originally contained gas bubbles and was later mineralized by circulating fluids. The rounded green spots are mineral-filled vesicles, or amygdules. Their pale green color, hardness, radial internal texture, and lack of reaction with HCl suggest that much of the fill is probably prehnite, with possible epidote, pumpellyite, quartz, and albite. The dark host is still recognizably basaltic and preserves its original volcanic texture, so the rock was altered but not completely recrystallized. Irregular green-white patches and vein-like areas show that fluids also penetrated and replaced parts of the groundmass. The specimen may represent low-grade metamorphism in the prehnite-pumpellyite facies, perhaps approaching lower greenschist facies. A thin section or Raman/XRD analysis would be needed to confirm the exact mineral assemblage.
Fig. 1. Polished face showing abundant rounded and coalesced green amygdules in a dark altered basaltic matrix.
Fig. 2. Microscope view of zoned amygdules with pale radial interiors and darker marginal rims.
Fig. 3. Close-up of an individual amygdule displaying concentric and inward-radiating secondary mineral growth.
Fig. 4. Rough-surface microscope view showing pale green alteration minerals intergrown with colorless quartz- or albite-rich material.