The distinction of analcime from leucite in rocks by X-ray methods

Since W. Lindgren first detected the presence of microphenocrysts of analcime in basalt, many observers have recorded this mineral as a constituent of igneous rocks, but there is some difficulty in distinguishing between analcime and glass and between analcime and leucite in thin rock-sections. For instance, H. Rosenbusch identified the interstitial colourless isotropic material in monchiquites as glass, whereas L. V. Pirsson showed it to be analcime. H.S. Washington showed that basalts from Sardinia, previously thought to be leueitic, contain phenocrysts of analcime. A. Lacroix also found, in his study of north African basaltic lavas, that in many cases so-called leucite-lavas actually contain analcime and not leucite.