Basalt recovered from Hole 1153A between 243.0 and 274.9 mbsf (1.77 m) was assigned to a single lithologic unit that consists of slightly altered, medium gray aphyric pillow basalt. Vesicles are rare (<1%) and small (<1 mm). Although generally spherical, some vesicles are elongated, especially in Section 187-1153A-8R-2. Microphenocrysts of acicular plagioclase as long as 2.5 mm can be seen in hand specimen throughout Section 187-1153A-8R-2 and in some places in Section 187-1153A-8R-1. Microphenocrysts of skeletal olivine <0.4 mm are also present. Glassy rinds and/or chilled pillow margins occur on ~20% of the 32 pieces. Glass thickness is generally <2 mm, except for Sample 187-1153A-8R-1 (Piece 14), which is predominantly glass and is 2 cm thick. Groundmass texture in the pillow margins varies from glassy to intersertal, indicating rapid cooling. Spherulites (~1.5 mm diameter) are visible in hand specimen and associated with glassy rinds (e.g., Section 187-1153A-8R-1 [Piece 13]) (Fig. F1). These quench textures are highlighted by the alteration of the groundmass to a mixture of smectite and Fe oxyhydroxides. The thin section taken from Sample 187-1153A-7W-4 (Piece 3) illustrates the appearance of plagioclase sheaf textures (e.g., Fig. F2) within the glassy rind, which grades into a spherulitic zone toward the exterior of the chilled margin. Microlites of "Chinese lantern" olivine are also commonly associated with the chilled margins. Assessing relative proportions of groundmass phases in the chilled margins is impossible because the groundmass is cryptocrystalline. Fractures present in ~80% of the core are typical of pillow basalts, generally being either parallel or orthogonal to the pillow rims. Many of the pieces recovered are bounded by fracture surfaces and have V-shaped forms as described in "Igneous Petrology" in the "Site 1152," chapter.