Formula: NaCa2Al5Si5O20.6H2O Orthorhombic
Description: Thomsonite-Ca is a member of the zeolite group often found in radiating clusters of varying color in the amygdules of volcanic rocks.
IRON COUNTY: Thomsonite-Ca occurs abundantly in outcrops of the Porcupine volcanics along the Montreal River below the dam along Saxon flowage. The thomsonite occurs as coarse radiating bladed crystals in cavities and veins associated with lava flow tops. (Cannon, 1996). Recent XRD and energy dispersive x-ray analyses on some of this material shown that at least some of this material is natrolite. (W. Cordua, 2014 personal notes).