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519583 
Journal Article 
Compounds of the crandallite-type: Synthesis, properties and thermodynamic data of Ca-Sr-Ba-Pb-(arseno)-woodhouseites 
Schwab, RG; Pimpl, T; Schukow, H; Stolle, A; Breitinger, DK 
2005 
1 
Neues Jahrbuch fuer Mineralogie. Abhandlungen
ISSN: 0077-7757 
181 
3 
207-218 
English 
The pure M2+-(arseno)-woodhouseites with M2+ = Ca2+, Sr2+, Ba2+ and Pb2+ were synthesized at 200 degrees C/15 bar starting from the pure (hydr-)oxides and acids. The lattice constants were determined by x-ray powder diffraction and the Standard Free Energies of Formation Delta G(f,333)(0) (resp. mu(333)(0)) through dissolution equilibria at 333 K. They are for Sr-wood (svanbergite) a(0) = 699.1 +/-.1 [pm] c(0) = 1663.5 +/-.4 [pm] Delta G(f,333)(0) = -1269.3 +/- 3 [kcal center dot mol(-1)] Sr-As-wood (kemmlitzite) a(0) = 705.0 +/-.1 [pm] c(0)= 1693.6 +/-.2 [pm] Delta G(f,333)(0) = -1175.6 +/-.2 [kcal center dot mol(-1)] Ba-wood (no name) a(0) = 700.1.+/- 1 [pm] c(0) = 1732.0 +/- 3 [pm] Delta G(f,333)(0)= -1270.5 +/-.4 [kcal center dot mol(-1)] Ba-As-wood (weilerite) a(0) = 705.7 +/- 1 [pm] c(0) = 1746.9.2 [pm] Delta G(f,333)(0) = -1175.9 +/- 3 [kcal center dot mol(-1)] Pb-wood (hinsdalite) a(0) = 701.2.+/- 1 [pm] c(0) = 1683.1 +/-.2 [pm] Delta G(f,333)(0) = -1142.8 +/-.4 [kcal center dot mol(-1)] Pb-As-wood (hidalgoite) a(0) = 706.1.1 [pm] c(0) = 1705.0 +/-.3 [pm] Delta G(f,333)(0) = -1050.7 +/-.4 [kcal center dot mol(-1)] Ca-As-wood (arsenowoodhouseite) a(0) = 702.9 +/-.1 [pm] c(0) = 1648.4.2 [pm] Delta G(f,333)(0) = -1175.6 +/-.3 [kcal center dot mol(-1)] The dehydration temperatures are: Sr-wood (svanbergite) 480, 630 degrees C Pb-wood (hinsdalite) 575, 610 degrees C Sr-As-wood (kemmlitzite) 630, 645 degrees C Pb-As-wood (hidalgoite) 615 degrees C Ba-wood (no name) 525, 610 degrees C Ca-As-wood (arsenowoodhouseite) 590, 650 degrees C Ba-As-wood (weilerite) 580, 600 degrees C The corresponding 2d and 3d Garrel diagrams (model systems) show a generally higher thermodynamic stability of the arsenowoodhouseites. In the crand-wood mixed crystals Ca2+ and Sr2+ behave extremely antagonistic: Ca2+ favours the sulphate (wood), Sr2+ the phosphate (crand) component. In pure woodhouseites Ca2+ and Sr2+ exhibit an almost identical geochemical behaviour, however. The model systems can be used for the interpretation of natural element distribution patterns. In case of the lateritic weathering zone the behaviour of the ions and the formation of table-mountains connected with certain types of parent rocks and deposits (gold) can be explained perfectly. 
woodhouseites; arsenowoodhouseites; Standard Free Energy of Formation; lattice constants; Garrel diagrams; dissolution equilibria; thermodynamic data; lateritic weathering; table-mountains; crystal-structure; alunite-jarosite; australia; minerals; plumbogummite; queensland; phosphates; sr; pb; ba