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NaCa2Si3O8(OH)
Triclinic
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| Figure 17-20. Crystal drawing of pectolite from Franklin. Drawing is from Palache (1935) who provided crystallographic data. | ||
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Pectolite is known from several Franklin assemblages, but has not been reported from Sterling Hill. The extant data are those of Palache (1935) and Schaller (1955).
Franklin pectolite from the first assemblage noted below is white, with vitreous luster, and a fibrous habit. Habits vary substantially and include the grains and crystals described by Palache (1935). Peacock (1935), using Palache’s unpublished data, added the forms {120} and {120} to those listed by Palache (1935). Optically, it is biaxial, positive, with a = 1.604, b = 1.610, and g = 1.636; dispersion is perceptible, r > v. In shortwave ultraviolet the fluorescence is strong yellow-orange.
Pectolite is a sodium calcium silicate mineral of the pyroxenoid group. The extant analysis of Franklin pectolite is that given by Palache (1935) and not repeated here.
Franklin pectolite occurs in massive aggregates of prehnite, garnet, franklinite, and minor margarosanite. The assemblage is commonly sheared, and, in some specimens, pectolite is apparently being replaced by prehnite. It is also found in a recrystallized assemblage with roeblingite (Dunn et al., 1983a).
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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This
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