Plate P5. 4. Black to dark brown smectite vein cutting gabbro. Vein has sharp margins but tends to follow grain boundaries. At one point it has bifurcated and enclosed a piece of plagioclase. The small, white veinlet cutting the smectite is a late-stage crack filled with carbonate (Sample 176-735B-133R-7, 92-98 cm). All scale bars = 1 mm.