Perez-Pariente et al., "Ion-exchange in natural zeolite stilbite
and significance in defluoridation ability," Microporous and Mesoporous Materials, vol.
Qualitative XRD analysis led to identifying a variety of zeolite species, including analcime, as the dominant zeolytic phase, followed by chabazite, natrolite, thomsonite, wairakite, stilbite
, stilbite-Ca, phillip-site and stellerite-Na, thomsonite-Ca, chabazite-Ca and chabazite-Na, with minor stellerite, laumontite, levyne, phillipsite-Na, and gyrolite Other secondary minerals associated with zeolites were celadonite (Fe-rich mica), nontronite (Fe-rich smectite), greigeite (iron sulide mineral), koninckite or bobierrite (phosphates), alunite (sulphate), truscottite (silicate), calcite or dolomite, and quartz Nontronite occurred in most samples.
We note that whereas the clinopyroxene is fresh, the plagioclase is variably altered to albite and stilbite
. The mesostasis contains altered glass (i.e., hydrous Fe-Mg clays and micas), quenched Fe-Ti oxides, and Fe-rich pyroxenes and is similar petrographically to mesostasis textures described by Kontak et al.
A basalt quarry near the town of Sambava is the site of Madagascar's first known occurrence of calcite, stilbite
, laumontite and heulandite in fine specimens.
They are "heulandite" (heulandite sensu stricto and clinoptilolite), chabazite, analcime, stilbite
, barrerite, epistilbite, gmelinite, laumontite, natrolite, mesolite, scolecite, stellerite, tetranatrolite, thomsonite, and wairakite.
Victor's pieces show intricate, generally triangular, multiple twins of the transparent, pale yellow to yellow-brown calcite, some crystals hosting snowy excrescences of tiny stilbite
and laumontite crystals.
From the Komsomol mine: clusters of green ktenasite microcrystals; acicular tufts of white thaumasite; tabular apophyllite crystals to 5 cm, some of them water-clear or showing growth zones; transparent, rhombohedral crystals of calcite in clusters to 5 cm; white okenite "puff balls" to 6 mm; attractive clusters of orange stilbite
crystals to 6 cm; clusters of attractive pink laumontite to 6 mm; and sharp, lustrous pyrite crystals on pink apophyllite-encrusted matrix to 8 cm across.
Although not a major producer of collector-quality specimens, it has yielded fine examples of heulandite, stilbite
, calcite, chalcedony, datolite and prehnite.
Finally, clefts in gneiss along the very steep slopes of the Gasteinertal, at the eastern edge of the Hohe Tauern, are famous for good fluorite crystals, most of them octahedral but almost none of them pink, associated with small white stilbite
A few of the matrix specimens show associations of quartz, calcite and stilbite
. For the most part the andradite crystals are gemmy and of a luscious grass-green hue, although a few are greenish brown to yellowish brown.
Some "flowers" came out loose; others have small crystals of heulandite, stilbite
, analcime or calcite attached to their bases.
The common zeolites, including heulandite and stilbite
, are calcium-dominated minerals that are fairly high in silica.