HYDROXYAPOPHYLLITE

KCa₄Si₈O₂₀(OH).8H₂O
Tetragonal

Hydroxyapophyllite was first described from Franklin (as apophyllite) by Bauer and Berman (1930); it has not been studied since.

Description

	Figure  18-37. Crystal drawing of unanalysed apophyllite from the Palmer Shaft area in Franklin. The habit is not species-specific. Drawing is from Palache (1935) who provided crystallographic data.

Hydroxyapophyllite occurs as 3-5 mm euhedral, lustrous, light pink to colorless crystals. The crystals radiate from nodes. Bauer’s catalogue gives a measured density of 2.33 g/cm³.

Composition

Hydroxyapophyllite is a potassium calcium silicate hydroxide hydrate mineral. The only extant analysis is that of Bauer and Berman (1930), which yielded: SiO₂ 50.90, CaO 24.74, K₂O 3.70, Na₂O 0.42, MnO 0.47, ZnO 1.79, H₂O 17.71, total = 99.73     wt. %, indicating it is close to the (OH) end-member of the fluorapophyllite-hydroxyapophyllite series.

Occurrence and paragenesis

Bauer’s analyzed Franklin hydroxyapophyllite occurs as a mass of crystals, 6 x 10 cm in dimension, associated with minor calcite. It was reported to come from crumbly limestone (marble). A note in Bauer’s catalogue indicates it was found in April, 1924, on the 300 level at Franklin.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
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