STILBITE

NaCa₂Al₅Si₁₃O₃₆.14H₂O
Monoclinic

	Figure 19-7. Crystal drawing of twinned stilbite crystals from Sterling Hill. Drawing is from Palache (1935) who provided crystallographic data.

Stilbite is the most abundant of the zeolites at Franklin and Sterling Hill, yet it is a rare mineral. It was initially described by Palache (1928a) as epistilbite and was later shown by him (Palache, 1935) to be stilbite.

Description

Stilbite occurs in fine crystals, both as single euhedra and as twinned crystals as illustrated by Palache (1935)(Figure 19-7); crystals can be up to 1 cm in length. The habit is commonly radial, and fascicles from here resemble those from classic stilbite occurrences. Stilbite is colorless to light yellow, has perfect to imperfect cleavage, and a vitreous luster. There is no discernible fluorescence in ultraviolet.

Composition

Stilbite is a sodium calcium aluminum silicate hydrate mineral of the zeolite group. There are no analytical data for local specimens.

Occurrence and paragenesis

Stilbite was reported by Palache (1935) to occur at Franklin in altered pegmatite with epidote, actinolite, and calcite. Palache also reported several occurrences at Sterling Hill, one of which is on the 900 level, where it is associated with tennantite, epidote, actinolite, and titanite. Stilbite is the last mineral to form, coating tennantite crystals, which in turn postdate the other silicates. Stilbite was also found with heulandite and epidote on the 1300 level at Sterling Hill. Such material may have resulted from alteration of the core gneiss.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
Link to homepage
This page created: January 11, 2001