The solubility and behavior of lead in feldspar are elucidated by EPMA and X-ray photoelectron spectroscopy (XPS; also known as ESCA) analyses for green orthoclase (amazonite) from Broken Hill, New South Wales, Australia. The role in the crystal structure establishes Pb cation as PbAl₂Si₂O₈ endmember for the orthoclase solid solution, and the maximum quantity of PbAl₂Si₂O₈ is 3.8 mol% in the green orthoclase.
     The lead cations, except the one existing in the orthoclase lattice, namely structurally bound Pb, occur in the green orthoclase by the following two ways; 1) as galena inclusions, and 2) as unidentified Pb-bearing micro-inclusions. The chemical shift for Pb atom in the green orthoclase was investigated by XPS, and compared with those in a Pb-metal, Pb-oxides, and a galena. Differences in the binding energy between Pb in the green orthoclase and other Pb-substances show distinctly that most of the Pb is not present as impurities like micro-minerals, but as structural components in green orthoclase. Crystal chemical consideration of Pb affords us infallible discrimination of solubility of PbAl₂Si₂O₈ endmember rather than PbAlSi₃O₈. The existence of PbAl₂Si₂O₈ as the main endmember in green orthoclase exhibits the charge-coupled substitution in the extra framework and the tetrahedral site; K⁺+Si⁴⁺ ↔ Pb²⁺+Al³⁺.
     Inhomogeneous distribution of Pb cation within the single crystal shows that the condition of Pb cation in green orthoclase structure is unstable.

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