Mordenite

Mordenite is a high-silica zeolite, in which the Si,Al content of the framework and the cation content of the erionite cavities are moderately variable. Mordenite is a common alteration product of pyroclastic sediment and sedimentary rocks, as well as lava flows. Mordenite crystallizes over a range of physical conditions, as a replacement of volcanic glass or pre-existing zeolite phases, from the surface temperatures of lakes in arid climates.

Color: Colorless, white, yellowish, pinkish.

Hardness: 3-4 on Mohs scale.