Carlfrancisite
A valid IMA mineral species
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About Carlfrancisite
Dr. Carl Francis
Formula:
Mn2+3(Mn2+,Mg,Fe3+,Al)42[As3+O3]2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42
Colour:
Pale yellow to yellow-orange
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
3.620 (Calculated)
Crystal System:
Trigonal
Name:
Named in honor of Dr. Carl A. Francis [b.October 21, 1949], mineralogist and former curator of the Harvard University Mineralogical Museum (for 34 years). His professional interests include systematic mineralogy and the geology of pegmatites.
Unique Identifiers
Mindat ID:
43359
Long-form identifier:
mindat:1:1:43359:6
IMA Classification of Carlfrancisite
Approved
Approval year:
2012
First published:
2013
Type description reference:
Hawthorne, Frank C., Abdu, Yassir A., Ball, Neil A., Pinch, William W. (2013) Carlfrancisite: Mn2+3(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia. American Mineralogist, 98 (10) 1693-1696 doi:10.2138/am.2013.4426
Classification of Carlfrancisite
8.BE.45
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
E : With only medium-sized cations, (OH, etc.):RO4 > 2:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
E : With only medium-sized cations, (OH, etc.):RO4 > 2:1
43.4.9.3
43 : COMPOUND PHOSPHATES, ETC.
4 : Anhydrous Compound Phosphates, etc·, Containing Hydroxyl or Halogen
43 : COMPOUND PHOSPHATES, ETC.
4 : Anhydrous Compound Phosphates, etc·, Containing Hydroxyl or Halogen
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Cfc | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Carlfrancisite
Vitreous
Transparency:
Translucent
Comment:
Vitreous to opalescent
Colour:
Pale yellow to yellow-orange
Streak:
Very pale yellow
Hardness:
3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
Micaceous on {001}
Micaceous on {001}
Parting:
None observed
Fracture:
Hackly
Density:
3.620 g/cm3 (Calculated)
Optical Data of Carlfrancisite
Type:
Uniaxial (+)
RI values:
nω = 1.756(2) nε = 1.758(2)
Max. Birefringence:
δ = 0.002
Based on recorded range of RI values above.
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.
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).
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 uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Pleochroism:
Non-pleochroic
Comments:
Refractive indices for 590 nm using a gel filter.
Chemistry of Carlfrancisite
Mindat Formula:
Mn2+3(Mn2+,Mg,Fe3+,Al)42[As3+O3]2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42
Element Weights:
Crystallography of Carlfrancisite
Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
R3c
Cell Parameters:
a = 8.2238(2) Å, c = 205.113(6) Å
Ratio:
a:c = 1 : 24.941
Unit Cell V:
12,013.48 ų (Calculated from Unit Cell)
Z:
6
Twinning:
None observed.
Comment:
Space group R-3c assumed by Hawthoren (2018); Lake and Von Dreele (2025) conclude it is R3c (non-centrosymmetric).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.107 Å | (48) |
| 3.243 Å | (54) |
| 3.051 Å | (43) |
| 2.918 Å | (47) |
| 2.826 Å | (100) |
| 2.676 Å | (63) |
| 2.371 Å | (88) |
| 1.552 Å | (84) |
Reference:
Hawthorne, Frank C., Abdu, Yassir A., Ball, Neil A., Pinch, William W. (2013) Carlfrancisite: Mn2+3(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia. American Mineralogist, 98 (10) 1693-1696 doi:10.2138/am.2013.4426
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Carlfrancisite
General Appearance of Type Material:
Curved platy aggregates ~2 cm across.
Place of Conservation of Type Material:
In the collections of the Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada, catalogue number M56375.
Geological Setting of Type Material:
Metamorphosed lenses associated with Cu-Pb-Ag sulfide ores in feldspathic sandstone that have subsequently been reworked by late hydrothermal solutions.
Associated Minerals at Type Locality:
Reference:
Hawthorne, Frank C., Abdu, Yassir A., Ball, Neil A., Pinch, William W. (2013) Carlfrancisite: Mn2+3(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia. American Mineralogist, 98 (10) 1693-1696 doi:10.2138/am.2013.4426
Synonyms of Carlfrancisite
Other Language Names for Carlfrancisite
Common Associates
Associations Based on Photo Data:
| 3 photos of Carlfrancisite associated with Garpenbergite | Mn6◻AsSbO10(OH)2 |
| 2 photos of Carlfrancisite associated with Dolomite | CaMg(CO3)2 |
| 1 photo of Carlfrancisite associated with Jacobsite | Mn2+Fe3+2O4 |
| 1 photo of Carlfrancisite associated with Alleghanyite | Mn2+5(SiO4)2(OH)2 |
| 1 photo of Carlfrancisite associated with Kutnohorite | CaMn2+(CO3)2 |
| 1 photo of Carlfrancisite associated with Stibarsen | AsSb |
| 1 photo of Carlfrancisite associated with Paradocrasite | Sb2(Sb,As)2 |
Related Minerals - Strunz-mindat Grouping
| 8.BE.05 | Augelite | Al2(PO4)(OH)3 |
| 8.BE.10 | Grattarolaite | Fe3+3(PO4)O3 |
| 8.BE.15 | Cornetite | Cu3(PO4)(OH)3 |
| 8.BE.20 | Clinoclase | Cu3(AsO4)(OH)3 |
| 8.BE.25 | Gilmarite | Cu3(AsO4)(OH)3 |
| 8.BE.25 | Arhbarite | Cu2Mg(AsO4)(OH)3 |
| 8.BE.30 | Flinkite | Mn2+2Mn3+(AsO4)(OH)4 |
| 8.BE.30 | Argandite | Mn7(VO4)2(OH)8 |
| 8.BE.30 | Raadeite | Mg7(PO4)2(OH)8 |
| 8.BE.30 | Allactite | Mn2+7(AsO4)2(OH)8 |
| 8.BE.35 | 'Mineral E (of Dunn, et. al., 1982)' | |
| 8.BE.35 | Chlorophoenicite | (Mn,Mg)3Zn2(AsO4)(OH,O)6 |
| 8.BE.35 | Magnesiochlorophoenicite | (Mg,Mn)3Zn2(AsO4)(OH,O)6 |
| 8.BE.40 | Gerdtremmelite | (Zn,Fe)(Al,Fe)2(AsO4)(OH)5 |
| 8.BE.45 | Dixenite | CuMn2+14Fe2+(SiO4)2(As5+O4)(As3+O3)5(OH)6 |
| 8.BE.45 | Mcgovernite | Mn19Zn3(AsO4)3(AsO3)(SiO4)3(OH)21 |
| 8.BE.45 | Hematolite | (Mn,Mg,Al,Fe3+)15(As5+O4)2(As3+O3)(OH)23 |
| 8.BE.45 | Turtmannite | (Mn,Mg)22.5Mg3-3x((V5+,As5+)O4)3(As3+O3)x(SiO4)3O5-5x(OH)20+x |
| 8.BE.45 | Arakiite | (Zn,Mn2+)(Mn2+,Mg)12(Fe3+,Al)2(As5+O4)2(As3+O3)(OH)23 |
| 8.BE.45 | Kraisslite | Zn3(Mn,Mg)25(Fe3+,Al)(As3+O3)2[(Si,As5+)O4]10(OH)16 |
| 8.BE.50 | Synadelphite | Mn2+9(As5+O4)2(As3+O3)(OH)9 · 2H2O |
| 8.BE.55 | Holdenite | (Mn2+,Mg)6Zn3(AsO4)2(SiO4)(OH)8 |
| 8.BE.60 | Kolicite | Mn2+7Zn4(AsO4)2(SiO4)2(OH)8 |
| 8.BE.65 | Sabelliite | (Cu,Zn)2Zn(AsO4,SbO4)(OH)3 |
| 8.BE.70 | Jarosewichite | Mn2+3Mn3+(AsO4)(OH)6 |
| 8.BE.75 | Theisite | Cu5Zn5(AsO4,SbO4)2(OH)14 |
| 8.BE.80 | Coparsite | Cu4(AsO4,VO4)O2Cl |
| 8.BE.85 | Waterhouseite | Mn2+7(PO4)2(OH)8 |
| 8.BE.90 | Vasilseverginite | Cu9O4(AsO4)2(SO4)2 |
Fluorescence of Carlfrancisite
Not fluorescent.
Other Information
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 Carlfrancisite
mindat.org URL:
https://www.mindat.org/min-43359.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Carlfrancisite
Reference List:
Williams, P. A., Hatert, F., Pasero, M., Mills, S. J. (2012) New minerals and nomenclature modifications approved in 2012. CNMNC Newsletter No 14. Mineralogical Magazine, 76 (5) 1281-1288 doi:10.1180/minmag.2012.076.5.15
Hawthorne, Frank C., Abdu, Yassir A., Ball, Neil A., Pinch, William W. (2013) Carlfrancisite: Mn2+3(Mn2+,Mg,Fe3+,Al)42(As3+O3)2(As5+O4)4[(Si,As5+)O4]6[(As5+,Si)O4]2(OH)42, a new arseno-silicate mineral from the Kombat mine, Otavi Valley, Namibia. American Mineralogist, 98 (10) 1693-1696 doi:10.2138/am.2013.4426
Hawthorne, Frank C. (2018) Long-range and short-range cation order in the crystal structures of carlfrancisite and mcgovernite. Mineralogical Magazine, 82 (5) 1101-1118 doi:10.1180/minmag.2017.081.098
Localities for Carlfrancisite
Showing 3 localities.
symbol to view information about a locality.
The Locality List
- 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).
All localities listed without proper references should be considered as questionable.
Namibia (TL) | |
| Williams et al. (2012) +2 other references |
Sweden | |
| Natural History Museum |
| Natural History Museum |
Quick NavTopAbout CarlfrancisiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatFluorescence Other InformationInternet Links References Localities Locality List
E15-11 south stope, 11 level, Asis West sector, Kombat Mine, Kombat, Otavi Constituency, Otjozondjupa Region, Namibia