Aspedamite

Aspedamite is a very rare mineral, one of two natural heteropolyniobates.^[1] Its chemical formula (one of the possible formulas) is complex and shows the presence of essential vacancies: []₁₂(Fe³⁺₂Fe²⁺)Nb₄(ThNb₉Fe³⁺₂Ti⁴⁺O₄₂)(H₂O)₉(OH)₃. Its structure (isometric, space group Im3) is the same as of the second known heteropolyniobate - menezesite.^[2][3] Aspedamite is somewhat similar to another mineral from Norway, peterandresenite, which is a hexaniobate.^[4]

Aspedamite
General
Category	Mineral
Formula (repeating unit)	[]12(Fe3+2Fe2+)Nb4(ThNb9Fe3+2Ti4+O42)(H2O)9(OH)3
IMA symbol	Apd
Identification
Color	Brownish orange to deep red
Cleavage	None Observed
Luster	Adamantine
Streak	Very pale orange
Specific gravity	4.070

References

1. "Aspedamite: Aspedamite mineral information and data". Mindat.org. Retrieved 2016-03-04.
2. Cooper, M.A., Abdu, Y.A., Ball, N.A., Černý, P., Hawthorne, F.C., and Kristiansen, R., 2012. Aspedamite, Ideally []₁₂(Fe³⁺,Fe²⁺)₃Nb₄[Th(Nb,Fe³⁺)₁₂O₄₂]₁₂{(H₂O),(OH)}₁₂, a New Heteropolyniobate Mineral Species from the Herrebøkasa Quarry, Aspedammen, Østfold, Southern Norway: Description and Crystal Structure. The Canadian Mineralogist 50, 793-804; DOI: 10.3749/canmin.50.4.793
3. "Menezesite: Menezesite mineral information and data". Mindat.org. Retrieved 2016-03-04.
4. "Peterandresenite: Peterandresenite mineral information and data". Mindat.org. Retrieved 2016-03-04.