We don't have synonyms for nepheline yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are nephelium, nephelite and orpheline.
(n) :
(mineralogy) A feldspathoid mineral of silica-poor igneous, plutonic and volcanic rocks. Chemically, nepheline is a plagioclase feldspar with insufficient silica to satisfy the chemical bonds. Because of the unfilled bonds, nepheline weathers rapidly and can only be seen as inclusions in freshly broken rock.
(n) :
(mineralogy) A feldspathoid mineral of silica-poor igneous, plutonic and volcanic rocks. Chemically, nepheline is a plagioclase feldspar with insufficient silica to satisfy the chemical bonds. Because of the unfilled bonds, nepheline weathers rapidly and can only be seen as inclusions in freshly broken rock.