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Thermal stability of crandallite CaAl3(PO4)2(OH)5•(H2O) – a ‘cave’ mineral from the Jenolan Caves

Frost, Ray L., Palmer, Sara J., & Pogson, Ross (2012) Thermal stability of crandallite CaAl3(PO4)2(OH)5•(H2O) – a ‘cave’ mineral from the Jenolan Caves. Journal of Thermal Analysis and Calorimetry, 107(3), pp. 905-909.

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Abstract

Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral crandallite CaAl3(PO4)2(OH)5•(H2O) and to ascertain the thermal stability of this ‘cave’ mineral. X-ray diffraction proves the presence of the mineral and identifies the products after thermal decomposition. The mineral crandallite is formed through the reaction of calcite with bat guano. Thermal analysis shows that the mineral starts to decompose through dehydration at low temperatures at around 139°C while dehydroxylation occurs over the temperature range 200 to 700°C with loss of OH units. The critical temperature for OH loss is around 416°C and above this temperature the mineral structure is altered. Some minor loss of carbonate impurity occurs at 788°C. This study shows the mineral is unstable above 139°C. This temperature is well above the temperature in caves, which have a maximum temperature of 15°C. A chemical reaction for the synthesis of crandallite is offered and the mechanism for the thermal decomposition is given.

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3 citations in Scopus
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ID Code: 48763
Item Type: Journal Article
Keywords: thermogravimetric analysis, crandallite, ‘cave’ mineral, brushite, mundrabillaite, archerite.
DOI: 10.1007/s10973-011-1578-6
ISSN: 1388-6150
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Structural Chemistry and Spectroscopy (030606)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2012 Akademiai Kiado Rt.
Deposited On: 21 Feb 2012 08:52
Last Modified: 10 May 2014 21:40

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