Which Feldspar Has Exsolution Lamellae?

Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi₃O₈, in composition) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar (near albite, NaAlSi₃O₈, in composition).

Does potassium feldspar have lamellae?

Potassium feldspar (also orthoclase feldspar or K-spar) exhibits bands of different color on cleavage surfaces. These bands, or exsolution lamellae, are planar zones of slightly different composition.

Does plagioclase feldspar have exsolution lamellae?

Plagioclase feldspars

The play of colors visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae known as Bøggild intergrowth. The specific gravity in the plagioclase series increases from albite (2.62) to anorthite (2.72–2.75).