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Middlebackite

A valid IMA mineral species
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05128540017272472648980.jpg
Middlebackite

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
05199350017272013232086.jpg
Middlebackite, etc.

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
08585710017272472649361.jpg
Middlebackite

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
00403780017272013217847.jpg
Middlebackite

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
03906680017866585662702.jpg
Middlebackite, etc.

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
07728390017866582572667.jpg
Middlebackite

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
00403780017272013217847.jpg
Middlebackite

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
05199350017272013232086.jpg
Middlebackite, etc.

Val Gardena Sandstone exposure, San Lugano pass, Carano, Ville di Fiemme, Trento Province, Trentino-Alto Adige/Südtirol, Italy
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About MiddlebackiteHide

Formula:
Cu2C2O4(OH)2
Colour:
Turquoise-blue
Lustre:
Vitreous
Hardness:
2
Specific Gravity:
3.64 (Calculated)
Crystal System:
Monoclinic
Name:
For the Middleback Range, in which the type locality is situated.
Compare moolooite and fiemmeite; antipinite and wheatleyite.


Unique IdentifiersHide

Mindat ID:
47562
Long-form identifier:
mindat:1:1:47562:6

IMA Classification of MiddlebackiteHide

Classification of MiddlebackiteHide

Strunz-mindat (2026):
10.AB.50

10 : ORGANIC COMPOUNDS
A : Salts of organic acids
B : Oxalates

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
MbkIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of MiddlebackiteHide

Lustre:
Vitreous
Transparency:
Translucent
Colour:
Turquoise-blue
Streak:
Pale blue
Hardness:
2 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Fracture:
Irregular/Uneven
Density:
3.64 g/cm3 (Calculated)
Comment:
Calculated based on empirical formula

Optical Data of MiddlebackiteHide

Type:
Biaxial (+)
RI values:
nα = 1.663(4) nβ = 1.748(4) nγ = 1.861(4)
2V:
Calculated: 86.7°
Max. Birefringence:
δ = 0.198
Based on recorded range of RI values above.

Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.

Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.

Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.

Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).

This shows the grain boundary and Becke line effect under plane-polarised light, based on the contrast between this mineral's average refractive index and the mounting medium. It does not take into account mineral colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure - the conoscopic view for a grain cut perpendicular to the acute bisectrix, using this mineral's 2V. The two small white dots mark the melatopes - the points where the two optic axes emerge - and are shown only when they fall within the field of view. The coloured bands are isochromatics, and the dark bands are isogyres.

Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
slight, r>v
Pleochroism:
Visible
Comments:
X = colourless, Y = very pale blue, Z = dark sky blue; Z>Y>X

Chemistry of MiddlebackiteHide

Mindat Formula:
Cu2C2O4(OH)2
Element Weights:
Element% weight
Cu51.015 %
O38.533 %
C9.642 %
H0.809 %

Calculated from ideal end-member formula.
Cu
O
C
H
Elements listed:
C, Cu, H, O - search for minerals with similar chemistry

Crystallography of MiddlebackiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Setting:
P21/c

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
7.070 Å(16)
3.739 Å(100)
2.860 Å(18)
2.481 Å(12)
2.350 Å(9)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere<0.6
53 : Other minerals with taphonomic origins<0.4

Type Occurrence of MiddlebackiteHide

Type Locality:
ⓘ Iron Monarch Main Pit, Iron Knob, Pastoral Unincorporated Area, South Australia, Australia
General Appearance of Type Material:
Aggregates of blue prismatic crystals up to 0.3 mm across. Individual crystals are up to 0.05 mm long.
Place of Conservation of Type Material:
South Australian Museum, Adelaide, South Australia, Registration number G34300.
Associated Minerals at Type Locality:
AtacamiteMottramite
Reference:
Elliott, Peter (2019) Middlebackite, a new Cu oxalate mineral from Iron Monarch, South Australia: Description and crystal structure. Mineralogical Magazine, 83 (3) 427-433 doi:10.1180/mgm.2018.136

Synonyms of MiddlebackiteHide

Other Language Names for MiddlebackiteHide

Common AssociatesHide

Associations Based on Photo Data:
3 photos of Middlebackite associated with MalachiteCu2(CO3)(OH)2
1 photo of Middlebackite associated with AnglesitePbSO4
1 photo of Middlebackite associated with OliveniteCu2(AsO4)(OH)

Related Minerals - Strunz-mindat GroupingHide

10.AB.Deveroite-(Ce)Ce2(C2O4)3 · 10H2OMon. 2/m : P21/c
10.AB.EdwindavisiteCu(C2O4)(NH3)Orth. mmm(2/m2/m2/m) : Pbca
10.AB.XFalottaiteMnC2O4 · 3H2OOrth. mmm(2/m2/m2/m)
10.AB.Uroxite [(UO2)2(C2O4)(OH)2(H2O)2] · H2OMon. 2/m : P21/c
10.AB.05KatsarositeZn(C2O4) · 2H2OMon. 2/m : B2/b
10.AB.05AndreybulakhiteNi(C2O4) · 2H2OMon. 2/m : B2/b
10.AB.05HumboldtineFe2+(C2O4) · 2H2OMon. 2/m : B2/b
10.AB.05LindbergiteMn2+(C2O4) · 2H2OMon. 2/m : B2/b
10.AB.10GlushinskiteMg(C2O4) · 2H2OMon. 2/m : B2/b
10.AB.15MoolooiteCu(C2O4) · nH2OOrth.
10.AB.20StepanoviteNaMgFe3+(C2O4)3 · 8-9H2OTrig. 3m : P3c1
10.AB.25MinguzziteK3Fe3+(C2O4)3 · 3H2OMon. 2/m : P21/c
10.AB.30WheatleyiteNa2Cu(C2O4)2 · 2H2OTric. 1 : P1
10.AB.35ZhemchuzhnikoviteNaMgAl(C2O4)3 · 8H2OTrig. 3m : P3c1
10.AB.40WeddelliteCa(C2O4) · (2.5-x)H2OTet. 4/m : I4/m
10.AB.45WhewelliteCa(C2O4) · H2OMon. 2/m : P21/c
10.AB.47FiemmeiteCu2(C2O4)(OH)2 · 2H2OMon. 2/m : P21/c
10.AB.50CaoxiteCa(C2O4) · 3H2OTric. 1 : P1
10.AB.52Metauroxite(UO2)2(C2O4)(OH)2(H2O)2Tric. 1 : P1
10.AB.55Oxammite(NH4)2(C2O4) · H2OOrth. 222 : P21212
10.AB.60NatroxalateNa2(C2O4)Mon. 2/m : P21/c
10.AB.60Phoxite(NH4)2Mg2(C2O4)(PO3OH)2(H2O)4Mon. 2/m : P21/c
10.AB.60Carboferriphoxite[(NH4)K(H2CO3)][Fe3+(HPO4)(H2PO4)(C2O4)]Tric. 1 : P1
10.AB.60Ferriphoxite[(NH4)2K(H2O)][Fe3+(HPO4)2(C2O4)]Mon. 2/m : P21/c
10.AB.65Coskrenite-(Ce)Ce2(SO4)2(C2O4) · 8H2OTric.
10.AB.70Levinsonite-(Y)(Y,Nd,La)Al(C2O4)(SO4)2 · 12H2OMon. 2/m
10.AB.75Zugshunstite-(Ce)(Ce,Nd,La)Al(C2O4)(SO4)2 · 12H2OMon. 2/m : B2/b
10.AB.80NovgorodovaiteCa2(C2O4)Cl2 · 2H2OMon. 2/m : B2/m

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Internet Links for MiddlebackiteHide

References for MiddlebackiteHide

Localities for MiddlebackiteHide

Showing 7 localities.

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Australia (TL)
 
  • South Australia
    • Pastoral Unincorporated Area
      • Iron Knob
Pring et al. (2000) +1 other reference
  • Western Australia
    • Upper Gascoyne Shire
mineral middlebackite [Cu2C2O4 (OH) +4 other references
O’Connor et al. (2019)
Italy
 
  • Trentino-Alto Adige/Südtirol
    • South Tyrol
      • Überetsch-Unterland (Oltradige-Bassa Atesina)
        • Aldein (Aldino)
          • Radein (Redagno)
            • Bletterbach Gorge
Ferretti et al. (2017)
    • Trento Province
      • Ville di Fiemme
        • Carano
          • San Lugano pass
Demartin et al. (2017) +3 other references
  • Veneto
    • Vicenza Province
      • Valli del Pasubio
Domenico Saccardo et al. (2019) +1 other reference
Rocchetti (2019: Aggiornamento 2019 sulla mineralogia vicentina. Moolooite e middlebackite di Valle Cumerlati.Studi e Ricerche - Associazione Amici del Museo - Museo Civico “G. Zannato”, 26, 46-47)
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