[ 'pleɪdʒɪə(ʊ)kleɪz , 'plagɪəʊ- ]
(also ~ feldspar )
■ noun a form of feldspar consisting of aluminosilicates of sodium and/or calcium, common in igneous rocks and typically white.
Origin
C19: from plagio- + Gk klasis 'cleavage' (because orig. characterized as having two cleavages at an oblique angle).