pyrope-spessartine series — a series between pyrope and spessartine; see pyrope-spessartine series in ‘Classification’ …
pyroxene — a large group of minerals …
pyrrhotite — species of mineral; data; faceted specimens reported (Iverson, 2012) …
quartz — species of mineral; see quartz in ‘Classification’ …
quartzite — a hard metamorphic rock which was originally pure quartz sandstone …
rainbow moonstone — variety of labradorite, anorthite; see rainbow moonstone in ‘Classification’ …
rainbow obsidian — variety of obsidian; see rainbow obsidian in ‘Classification’ …
rectangle — a shape in faceting a gemstone …
rhodizite — species of mineral; data; faceted specimens exist …
rhodochrosite — species of mineral; see rhodochrosite in ‘Classification’ …
rhodolite — variety of pyrope-almandine series; see rhodolite in ‘Classification’ …
rhodonite — species of mineral; see rhodonite in ‘Classification’ …
rhomboid — rare shape in faceting a gemstone …
rhyolite — an igneous rock of felsic composition …
rock crystal — variety of quartz; see rock crystal in ‘Classification’ …
romanèchite — species of mineral; data; constituent of the so-called psilomelane …
rose quartz — variety of quartz; see rose quartz in ‘Classification’ …
round — a commonly used shape in faceting a gemstone …
rubellite — variety of elbaite; see rubellite in ‘Classification’ …
ruby — variety of corundum; see ruby in ‘Classification’ …
