Electron Microscopy of Etched Plagiodase Feldspar

Single crystals of plagiodase feldspar were selectively etched by immersion in aqueous solutions of Na 2 CO 3 and K 2 CO 3 for 48 hr and in 48% HF for 1 to 3 sec. The etched surfaces are replicated using a two‐stage Formvar‐carbon replica shadowed with palladium. These replicas reveal that etching varies in different twin lamellas and that etch pits align along twin boundaries.