 |
| Titel |
Heterogenite vs asbolane: a mineralogical study of cobalt oxides from the DRC (Democratic Republic of the Congo) |
| VerfasserIn |
Christian Burlet, Yves Vanbrabant, Sophie Decree |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100380
|
| Publikation (Nr.) |
 EGU/EGU2014-16334.pdf |
|
|
|
|
|
| Zusammenfassung |
| The largest cobalt ore reserves are located in DRC, the Democratic Republic of Congo. Most
of cobalt is observed as black cobaltic oxide minerals: heterogenite [HCoO2] and asbolane
[(Ni,Co)2-xMn(O,OH)4.nH2O] which are hardly differentiable since they exhibit similar
macroscopic habit and textures. These minerals are frequently observed in similar
environment (oxidized horizon of ore deposits) and they are commonly poorly-crystallized
limiting their study with XRD. Their chemical composition is also not very well-constrained
since they exhibit significant chemical substitutions with cations as Cu, Co, Ni,
Mn.
Our observations on a set of heterogenite and asbolane samples from DRC combined with
samples from other localities shows that each phase, even under an amorphous form, can be
readily distinguished by Raman microspectrometry. This technique is therefore
attractive during ore deposit characterization campaigns or during the follow-up
extraction operations where it is important to distinguish the main constituting
Co-phase(s). The main advantage of this technique is its speed since no sample
preparation is required during the collection Raman spectra that usually last few tens of
seconds. The method provides information at a μm-scale and several points are
thus required to fully characterize ore batches composed of different mineralogical
phases.
Our petrographical observations show also that asbolane and heterogenite mineralogical
phases can coexist at a μm-scale as two distinct phases into ‘heterogenite’ ore.
The distinction between heterogenite and asbolane from our sample set can also
be conducted on a chemical base showing that heterogenite represents the richer
Co-phase with variable Cu concentrations. By contrast, only Mn traces are usually
observed in heterogenite minerals from DRC except in few samples, but always in
lower concentration than in asbolane. The latter shows variable Mn/(Mn+Co) ratio
between 0.85 and 0.3 and the decrease of this value is related to enrichment into
Cu.
PIC
Figure 1. Example of coexisting heterogenite (Het) and asbolane (Asb), with their
respective EDS spectrum.1
0.0.1 1Vanbrabant, Y., Burlet, C. and Louis, P., Mineralogical Characterization of
Cobaltic Oxides from the Democratic Republic of Congo, in Ni-Co 2013, John Wiley &
Sons, Inc., Hoboken, NJ, USA., Pages: 241–254, 2013 |
|
|
|
|
|
|