STILBITE
Stilbite is one of the many species belonging to the zeolite
group of minerals. Stilbite is a hydrous sodium calcium aluminosilicate
(NaCa2Al5Si13O36·14H2O).
As do all zeolites, stilbite tends to fill or partially fill voids (vesicles)
in volcanic lavas. Stilbite forms sheaths or bundles of crystals, often
as bowtie-shaped masses. It is usually whitish in color, but can also be
brownish, yellowish, or reddish.
Stilbite
(field of view ~4.0 cm across)
Stilbite
(pinkish-peach) & fluorapophyllite (pale blue), from India. Fluorapophyllite is a hydrous potassium
calcuim hydroxy-fluorosilicate (KCa4(F,OH)(Si8O20)·8H20).
(CM public display, Carnegie Museum of Natural
History, Pittsburgh, Pennsylvania, USA)
Stilbite
from Poona, India.