Saturday, July 23, 2005


Medium- to coarse-grained intrusive igneous rock, a member of the alkali-syenite group (see syenite) that consists largely of feldspar and nepheline. It is always considerably poorer in silica and richer in alkalies than granite. The extraordinarily varied mineralogy of the nephelinesyenites and their remarkable variation in habit, fabric, appearance, and composition


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