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.