Figure F47. Variation in intensity of alteration between typical basalt and fine-grained, chilled volcanic eruption breccia. A. Typical basalt consists of internal kernels of dusky red with some light brown-gray mottling. These are surrounded by dark halos (green) and a brown-orange halo adjacent to the vein. B. In the brecciated rock the alteration is much more chaotic. The intense fracturing facilitated the more intense and pervasive development of dark alteration halos.