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CaBSiO4(OH)
Monoclinic
Datolite, a calcium boron silicate hydroxide mineral, was first described by Penfield and Foote (1897) from the Parker Mine, but it is not known from Sterling Hill.
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| Figure 15-40. Crystal drawing of datolite of uncommon habit from Franklin. Drawing is from Palache (1935) who provided crystallographic data. | ||
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Datolite occurs as fine, colorless, euhedral crystals to several cm in vuggy, recrystallized assemblages. Crystal habits are complex (Figure 15-41); tabular crystals are known (Figure 15-40). The fine crystals from Franklin have been studied morphologically by Palache (1910), Ungemach (1911), Gordon (1923b), and Bauer and Berman (1930); these morphological works are summarized by Palache (1935).
Additional morphological description was provided by Richards (1989). Datolite is colorless to light pink, with vitreous luster, and no cleavage.
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| Figure 15-41. Crystal drawings of datolite from the Parker Shaft area in Franklin. Drawings are from Palache (1935) who provided crystallographic data. | ||
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Franklin datolite has been little studied in other repects and not at all chemically.
Datolite occurs in the recrystallized areas at Franklin. It occurs as single crystals and as druses; some are dull-lustered and some are bright. It also forms splendid crystals up to 1 cm in size; most are 1-2 mm. Botryoidal crusts of datolite, called botryolite, were found in 1926. Datolite commonly lines vugs in recrystallized assemblages and seams and occurs as druse botryoidal coatings on rhodonite, manganaxinite, and cahnite. The bulk of the extant specimens are composed of massive, medium- to fine-grained, vuggy aggregates of andradite, manganaxinite, mica, prehnite, nasonite, clinohedrite, impure hancockite, and other species, which were found near the Parker Dump in Franklin. Datolite is among the last minerals to form.
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| Copyright © 1995 by Pete J. Dunn |
Website
by Herb Yeates
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Link
to homepage
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This
page created: January 11, 2001 |
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