Thermal stability of the ‘cave’ mineral ardealite Ca2(HPO4)(SO4)•4H2O

Frost, Ray L., Palmer, Sara J., & Pogson, Ross (2012) Thermal stability of the ‘cave’ mineral ardealite Ca2(HPO4)(SO4)•4H2O. Journal of Thermal Analysis and Calorimetry, 107(2), pp. 549-553.

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Thermogravimetry combined with evolved gas mass spectrometry has been used to characterise the mineral ardealite and to ascertain the thermal stability of this ‘cave’ mineral.
The mineral ardealite Ca2(HPO4)(SO4)•4H2O is formed through the reaction of calcite with bat guano. The mineral shows disorder and the composition varies depending on the origin of the mineral. Thermal analysis shows that the mineral starts to decompose over the temperature range 100 to 150°C with some loss of water. The critical temperature for water loss is around 215°C and above this temperature the mineral structure is altered. It is concluded that the mineral starts to decompose at 125°C, with all waters of hydration being lost after 226°C. Some loss of sulphate occurs over a broad temperature range centred upon 565°C. The final decomposition temperature is 823°C with loss of the sulphate and phosphate anions.

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ID Code: 48213
Item Type: Journal Article
Refereed: Yes
Keywords: Raman spectroscopy, phosphate, sulphate, ardealite
DOI: 10.1007/s10973-011-1458-0
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: Past > Schools > Chemistry
Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2012 Springer Verlag
Copyright Statement: The original publication is available at
Deposited On: 24 Jan 2012 00:28
Last Modified: 09 May 2014 10:57

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