mogánite — species of mineral; constituent of chalcedony …
montebrasite — species of mineral; see montebrasite in ‘Classification’ …
monzonite — an igneous intrusive rock, composed of approximately equal amounts of plagioclase and alkali feldspar, with less than 5% quartz by weight …
moonstone — variety of orthoclase; see moonstone in ‘Classification’ …
morganite — variety of beryl; see morganite in ‘Classification’ …
morion — variety of smoky quartz, quartz; see morion in ‘Classification’ …
mtorolite — trade name of chrome-chalcedony …
musgravite — synonym of magnesiotaaffeite-6N’3S …
natrolite — species of mineral; see natrolite in ‘Classification’ …
nepheline — a rock-forming mineral, occurs in igneous rocks with low silica, and in their associated pegmatites …
nephrite — a rock; see nephrite in ‘Classification’ …
neptunite — species of mineral; data; faceted specimens exist …
nickeline — species of mineral; data; faceted specimens reported (Iverson, 2012) …
nickeloan magnesite — variety of magnesite; see nickeloan magnesite in ‘Classification’ …
nifontovite — species of mineral; data; faceted specimens exist …
nonagon — rare shape in faceting a gemstone …
nuummite — an unapproved name; metamorphic rock found in Greenland, consisting primarily of two species of amphiboles — anthophyllite and gedrite; ornamental stone; sometimes spelled ‘nuumite’ …
obsidian — a rock; see obsidian in ‘Classification’ …
octagon — a commonly used shape in faceting a gemstone …
