Intergrowths of levyne and offretite occur in vesicles of the Picture Gorge Basalt near Beech Creek, Oregon. Levyne occurs as aggregates of thin, platy crystals, and the offretite occurs as white, silky, fibrous layers on the levyne. The offretite fibers grew normal to the (0001) of levyne, and, locally, replaced the levyne. Electron microprobe analyses of the zeolites yielded the formulas Ca2.50Mg0.00Na0.58K0.27Al6.78Si11.46O36.nH2O for levyne and Ca1.79Mg0.17Na0.30K1.00Al0.08Si12.11O36.nH2O for offretite. Hexagonal cell parameters for the levyne are a = 13.356(3)Å, c = 22.88(1)Å,V=3,535(2)Å3; and for the offretite, a = 13.348(2)Å, c = 7.59(2) Å,V=1,172(3) Å3. Offretite had previously been recognized only from the type locality near Montbrison, France. Thus, the identification of offretite from the Beech Creek locality, as well as from other similar occurrences associated with levyne in basalts, indicates that it is not so rare as previously supposed.

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