1
24
R.L. Frost, S.J. Palmer / Thermochimica Acta 521 (2011) 121–124
the DTG curves. The following reaction is proposed to occur:
a sink for the free migration of phosphate into surroundings. The
implication is that these minerals are stable even if exposed to bush
fires.
Fe3 O(PO ) (SO ) → Fe O + 2FePO +2SO
+
4
4
2
4
2
3
4
4
3
4
. Conclusions
The two minerals diadochite and destinezite have the same
Acknowledgments
The financial and infra-structure support of the Queens-
land University of Technology, Chemistry discipline is gratefully
acknowledged. The Australian Research Council (ARC) is thanked
for funding the instrumentation.
3
+
formula Fe (PO )(SO )(OH)·6H O. Destinezite is the crystalline
2
4
4
2
material, whereas diadochite has been described as a colloidal min-
eral and displays amorphicity. The question must be asked: are
the two minerals identical. Such a question cannot be answered by
XRD. Thermal analytical techniques go someway to showing some
similarity in the two minerals. However, this is not definitive as
the thermal analysis patterns of the two minerals show significant
differences. Therefore, the question remains unanswered.
References
[
[
1] M. Foldvari, B. Nagy, Diadochite and destinezite from Martansentimre
Hungary], Foldtani Kozlony 115 (1985) 123–131.
2] M.Z. Fursova, Diadochite from the oxidation zone of the Karagaily polymetallic
deposit, Izvestiya Akademii Nauk Kazakhskoi SSR, Seriya Geologicheskaya 22
[
◦
For destinezite, two DTG peaks are observed at 129 and 182 C,
(
1965) 74–76.
and based upon the ion current curves are attributed to the loss
of water of hydration. For diadochite, a broad peak at 84 C is
attributed to this water mass loss. The thermal analysis patterns
of destinezite show small DTG peaks at 576 C attributed to a car-
bonate impurity. The thermal analysis patterns of diadochite show
an additional peak at 289 C, which is assigned to the loss of water
molecules trapped in the disordered structure. The higher temper-
ature mass losses at 685 C for destinezite and 655 C for diadochite
based upon the ion current curves are due to sulphate and phos-
phate decomposition. However, more sulphate anions are in the
structures, illustrated by the smaller multiplicity numbers used in
preparing the mass spectra.
[
3] L.D. German, Destinezite in the oxidation zone of the pyrite deposits of Blyava,
S. Ural, Zapiski Vserossiiskogo Mineralogicheskogo Obshchestva 85 (1956)
574–577.
◦
◦
[4] A.I. Ginzburg, The phosphates of granite pegmatites, Trudy Mineralogicheskogo
Muzeya, Akademiya Nauk SSSR (1952) 36–63.
[
5] V. Bouska, E.K. Lazarenko, Y.M. Melnik, E. Slanski, Destinezite, Acta Universitatis
Carolinae: Geologica (1960) 127–152.
◦
[
6] D.R. Peacor, R.C. Rouse, T.D. Coskren, E.J. Essene, Destinezite (“diadochite”),
Fe2(PO4)(SO4)(OH)·6H2O: its crystal structure and role as a soil mineral at Alum
Cave Bluff, Tennessee, Clays and Clay Minerals 47 (1999) 1–11.
◦
◦
[7] R. Sitzia, Infrared spectra of some natural phosphates, Rendiconti del Seminario
della Facolta di Scienze dell’Universita di Cagliari 36 (1966) 105–115.
[
8] E. Dittler, The origin of delvauxite, Chemie und Industrie der Kolloide 5 (1910)
5.
3
[9] K.A. Vakusevich, Mineral of the delvauxite type from recent sediments of the
Moscow Basin, Zapiski Vserossiiskogo Mineralogicheskogo Obshchestva 76
What this work has shown is that the two stoichiometrically
(
1947) 271–272.
related minerals destinezite and diadochite are quite stable up to
[
10] R. van Tassel, Autunite, apatite, delvauxite, evansite, and fluellite from the
Vis.acte.e region, Bulletin de la Societe Belge de Geologie, de Paleontologie et
d’Hydrologie 68 (1959) 226–248.
◦
2
00 C. These minerals are found in soils and function as a phos-
phate and sulphate sink. The origin of relatively stable destinezite
from diadochite gel-like medium in clayey parts of mineral dumps
and similar media including soils, thus represents the possibility of
phosphate/sulphate capture in the solid-solution phase and makes
[
[
11] W. Heyer, History and geology of the diadochite caves near Saalfeld (Saale),
Zeitschrift fuer Praktische Geologie 47 (1939) 165–168.
12] J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols, Handbook of Mineralogy,
Mineral Data Publishing, Tuscon, Arizona, USA, 2000.