Melt–Solid Dihedral Angles of Common Minerals in Natural Rocks

The melt–solid dihedral angle has been measured in a range of
\nigneous rock types, ranging in composition from picrite, through
\nbasalt, phonolite, andesite and rhyolite, for the minerals quartz,
\nleucite, plagioclase, olivine, amphibole and clinopyroxene. Populations
\nof up to 104 true 3-D angles were measured in each sample
\nusing a universal stage mounted on an optical microscope. The
\nmedian and standard deviation of the angle populations for each
\nmineral are distinct (plagioclase 25, with standard deviation
\n(SD) 11; clinopyroxene 38, with SD 14; olivine 29, with
\nSD 13; quartz 18, with SD 9; leucite 20, with SD 11),
\nwith no control by either melt composition or degree of approach of
\nthe grains to their equilibrium shapes.