English
Image:Nepheline.jpg|thumb|Nepheline
Noun
nepheline
- 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.
Chemical composition: Sodium potassium aluminum subsilicate, <math>(Na,K)(Al,Si)_2O_4</math>
Physical properties:
*Moh's Hardness: 5.5-6.0
*Specific gravity: 2.5-2.6
*Color: Colorless, white, gray, reddish, smoky; transparent to translucent
*Fracture: Subconchoidal
*Cleavage: Good prismatic
*Habit: Hexagonal-Hexagonal pyramidal
*Fluorescence: Often orange-red in portions of crystals
Related terms
feldspathoid, feldspar
zh:nepheline
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