nepheline

From Ancient Greek νεφέλη (nephélē, “cloud”), because crystals become cloudy when exposed to acid, +‎ -ine.

nepheline (countable and uncountable, plural nephelines)

1. (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.

• nephelite

• “Nepheline” in David Barthelmy, Webmineral Mineralogy Database, 1997–.
• “nepheline”, in Mindat.org‎, Hudson Institute of Mineralogy, accessed 29 August 2016.