This sample, which is physically indistinguishable from other chabazite-Ca specimens, consists of colorless, 1 to 2-mm rhombohedral crystals associated with heulandite-Ca and meionite. The sample also has the highest Mg content of all samples analyzed (0.34 apfu).
Cowlesite has been identified from a single occurrence (locality 48), where it forms lustrous white, silky, radiating crystal aggregates to 0.3 mm on a thin overgrowth of albite on a meionite crystal.
An erionite-series mineral intimately intergrown with levyne forms lustrous white to gray, silky, asbestiform, radial crystal aggregates to 0.3 mm on meionite at locality 48 (see cowlesite description above).
The mineral occurs both as euhedral, pseudotetragonal, bipyramidal, colorless to white, opaque crystals up to 5 mm, and as elongated anhedral growths replacing meionite fibers parallel to the c axis of the meionite.
At locality 30 this mineral was found as translucent white crystals up to 1 mm on altered meionite, microcline and other minerals in a 50 X 20 X 15-cm pocket in a sheared pegmatitic rock in contact with a diopside-carbonate metasediment.
At locality 52 it occurs as fibrous inclusions in phlogopite; at locality 21 it forms inclusions in heulandite-Ca; at locality 5 it appears as inclusions in chabazite-Ca; and at numerous localities it appears as overgrowths on and in cavities in meionite. Mesolite was identified by X-ray diffraction only, as its fibrous nature precluded its analysis by microprobe techniques.
Thomsonite occurs at localities 47 and 48 as bright white radiating tufts to 2 mm, porcelain-like growths on meionite exposed in cavities by the dissolution of calcite, or translucent tan spherical growths to 5 mm.
In the Grenville, dissolution of calcite, Na- and K-feldspars, meionite, nepheline and other rock-forming minerals probably contributed to the development of zeolites.
In FPS and other skarn deposits, zeolites occur in cavities in coarse-grained calcite, in joints and fractures in calc-silicate skarn and syenitic xenoliths, or as free-standing crystals on earlier-formed crystals of meionite, diopside, feldspars, titanite, fluorapatite, and other minerals that occur in cavities resulting from the dissolution of calcite once in contact with the skarn minerals.