RT Journal Article
T1 Interaction of phosphate-bearing solutions with gypsum: Epitaxy and induced twinning of brushite (CaHPO4·2H2O) on the gypsum cleavage surface
A1 Jorge Pinto, Andre Filipe
A1 Jiménez, Amalia
A1 Prieto, Manuel
AB Under slightly acidic conditions and 25 °C, the interaction between phosphate-rich aqueous solutions and gypsum cleavage fragments results in the surface precipitation of brushite (CaHPO4·2H2O) crystals, which grow epitaxially on the (010) surface of gypsum. Using an A-centered unit-cell setting for both brushite (Aa) and gypsum (A2/a), the epitaxial relationship implies matching of the planes (010) of both structures and correspondence between equivalent crystallographic directions within these planes. The crystal habit of the overgrowing brushite is thin tabular to laminar on {010} with {111̅} and {111} as side faces and a clear elongation on [101]. There are two orientations of the brushite plates on the gypsum surface related to each other by a twofold axis on [010]. Thus, the overgrowth is an aggregate of parallel brushite crystals that may be twin-related, with the twofold axis as the twin law. During the interaction, gypsum dissolution is coupled with brushite growth until saturation with respect to both minerals is reached. A model of this thermodynamically driven dissolution-crystallization process is presented using the geochemical code PHREEQC. The epitaxial relationships are explained by comparing the bond system and the crystallographic properties of both minerals.
PB Mineralogical Society of America
SN 0003-004X
YR 2009
FD 2009-01-02
LK https://hdl.handle.net/20.500.14352/101284
UL https://hdl.handle.net/20.500.14352/101284
LA eng
NO Pinto, A. J., et al. «Interaction of Phosphate-Bearing Solutions with Gypsum: Epitaxy and Induced Twinning of Brushite (CaHPO4{middle dot}2H2O) on the Gypsum Cleavage Surface». American Mineralogist, vol. 94, n.o 2-3, febrero de 2009, pp. 313-22. DOI.org (Crossref), https://doi.org/10.2138/am.2009.3046.
NO European Union
NO Ministerio de Educación y  Ciencia (España)
DS Docta Complutense
RD 3 abr 2025