Figure F115. Photomicrographs of Sample 206-1256D-20R-1, 27-29 cm (plane polarized light). A. Hyaloclastite showing fresh (pale brown) and altered (dark brown) glass. Fresh glass shards are surrounded by a rim of glass altered to clay minerals (field of view = 10 mm). B. Detail of glass alteration boundary. Note the smooth, banded alteration front (field of view = 2.5 mm).

Figure F115. Photomicrographs of Sample 206-1256D-20R-1, 27-29 cm (plane polarized light). A. Hyaloclastite showing fresh (pale brown) and altered (dark brown) glass. Fresh glass shards are surrounded by a rim of glass altered to clay minerals (field of view = 10 mm). B. Detail of glass alteration boundary. Note the smooth, banded alteration front (field of view = 2.5 mm).