Pseudoleucites occur as phenocrysts in a
tinguaite porphyry in Cordon, Isabela.
Petrographic and x-ray diffraction
studies show that it is composed chiefly
of high sanidine (Or91Ab9)
and hexagonal kalsilite (Ks80Ne20).
Chemistry and xray data point to a
transformation of highly potassic
leucite starting material to component
sanidine and kalsilite. Stoichiometric
relationships do not support a simple
breakdown or reaction mechanism. The
addition of silica to form sanidine
along with the possible removal of
kalsilite may explain the resultant
composition of the pseudoleucite.
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