Achyrophanite
A valid IMA mineral species
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About Achyrophanite
Formula:
(K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5
Colour:
straw-yellow to golden yellow
Lustre:
Vitreous
Specific Gravity:
3.814 (Calculated)
Crystal System:
Orthorhombic
New structure type. The crystal structure of achyrophanite (solved from single-crystal XRD data, R = 4.47%) is unique. It is based on the octahedral-tetrahedral M-T-O pseudo-framework (M = Fe3+ with admixed Ti, Al, Mg, Na; T = As5+). Large-cation A sites (A = K, Na) are located in the channels of the pseudo-framework. The achyrophanite structure can be described as stuffed, with the defect heteropolyhedral pseudo-framework derivative of the orthorhombic Fe3+AsO4 archetype.
Chemically related especially to pansnerite, and also to edtollite and melanarsite.
Partial or complete pseudomorphs of arsenatrotitanite, ideally NaTiO(AsO4), sometimes together with bradaczekite NaCu4(AsO4)3, after crystals of achyrophanite.
Chemically related especially to pansnerite, and also to edtollite and melanarsite.
Partial or complete pseudomorphs of arsenatrotitanite, ideally NaTiO(AsO4), sometimes together with bradaczekite NaCu4(AsO4)3, after crystals of achyrophanite.
Unique Identifiers
Mindat ID:
52919
Long-form identifier:
mindat:1:1:52919:4
IMA Classification of Achyrophanite
Approved
IMA Formula:
(K,Na)3(Fe3+,Ti4+,Al,Mg)5O2(As5+O4)5
Approval year:
2018
Approval history:
Named from the Greek άχυρον, straw, and φαίνομαι, to appear, in allusion to its typical straw-yellow color and long prismatic habit of crystals.
Type description reference:
Pekov, Igor V.; Zubkova, Natalia V.; Koshlyakova, Natalia N.; Belakovskiy, Dmitry I.; Vigasina, Marina F.; Agakhanov, Atali A.; Britvin, Sergey N.; Turchkova, Anna G.; Sidorov, Evgeny G.; Zhegunov, Pavel S.; et al. (2025) Achyrophanite, (K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5, a New Mineral with the Novel Structure Type from Fumarolic Exhalations of the Tolbachik Volcano, Kamchatka, Russia. Minerals, 15 (7). doi:10.3390/min15070706
Classification of Achyrophanite
8.BF.30
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
F : With medium-sized and large cations, (OH, etc.):RO4< 0.5:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
F : With medium-sized and large cations, (OH, etc.):RO4< 0.5:1
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 |
|---|---|---|
| Aph | 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 Achyrophanite
Vitreous
Transparency:
Transparent
Colour:
Straw-yellow to golden yellow
Streak:
White
Tenacity:
Brittle
Cleavage:
Perfect
(001)
(001)
Fracture:
Irregular/Uneven
Comment:
parallel intergrowths of flattened acicular crystals are flexible and elastic.
Density:
3.814 g/cm3 (Calculated)
Optical Data of Achyrophanite
Type:
Biaxial (+)
RI values:
nα = 1.823(7) nβ = 1.840(7) nγ = 1.895(7)
2V:
Measured: 60° to 10°
Max. Birefringence:
δ = 0.072
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 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.
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:
weak, r > v.
Orientation:
elongation is negative.
Optical Extinction:
Extinction is straight
Pleochroism:
Weak
Comments:
Z (very pale yellow) > Y = X (colorless).
Chemistry of Achyrophanite
Mindat Formula:
(K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5
Element Weights:
Crystallography of Achyrophanite
Crystal System:
Orthorhombic
Class (H-M):
222 - Disphenoidal
Space Group:
P2221
Setting:
P2221
Cell Parameters:
a = 6.5824(2) Å, b = 13.2488(4) Å, c = 10.7613(3) Å
Ratio:
a:b:c = 0.497 : 1 : 0.812
Unit Cell V:
938.48 ų (Calculated from Unit Cell)
Z:
2
Twinning:
Achyrophanite is microtwinned: twinning by merohedry Class I with the twin domains ratio 53/47 was found in the studied crystal.
Comment:
new structure type
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 5.615 Å | (59) |
| 4.174 Å | (42) |
| 3.669 Å | (31) |
| 3.148 Å | (33) |
| 2.852 Å | (43) |
| 2.814 Å | (100) |
| 2.689 Å | (29) |
| 2.237 Å | (28) |
Reference:
Pekov, Igor V.; Zubkova, Natalia V.; Koshlyakova, Natalia N.; Belakovskiy, Dmitry I.; Vigasina, Marina F.; Agakhanov, Atali A.; Britvin, Sergey N.; Turchkova, Anna G.; Sidorov, Evgeny G.; Zhegunov, Pavel S.; et al. (2025) Achyrophanite, (K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5, a New Mineral with the Novel Structure Type from Fumarolic Exhalations of the Tolbachik Volcano, Kamchatka, Russia. Minerals, 15 (7). doi:10.3390/min15070706
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45a : [Sulfates, arsenates, selenates, antimonates] |
Type Occurrence of Achyrophanite
General Appearance of Type Material:
long-prismatic to acicular or, rarer, tabular crystals up to 0.02 × 0.2 × 1.5 mm, which form parallel, radiating, bush-like, or chaotic aggregates up to 3 mm across
Place of Conservation of Type Material:
collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, registration number 5029/1
Geological Setting of Type Material:
The temperature in this area was ca. 430 °C sublimates of the Arsenatnaya fumarole
Associated Minerals at Type Locality:
Reference:
Pekov, Igor V.; Zubkova, Natalia V.; Koshlyakova, Natalia N.; Belakovskiy, Dmitry I.; Vigasina, Marina F.; Agakhanov, Atali A.; Britvin, Sergey N.; Turchkova, Anna G.; Sidorov, Evgeny G.; Zhegunov, Pavel S.; et al. (2025) Achyrophanite, (K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5, a New Mineral with the Novel Structure Type from Fumarolic Exhalations of the Tolbachik Volcano, Kamchatka, Russia. Minerals, 15 (7). doi:10.3390/min15070706
Synonyms of Achyrophanite
Other Language Names for Achyrophanite
Related Minerals - Strunz-mindat Grouping
| 8.BF. | Manganoarrojadite-(KNa) | (KNa)(NaNa)Mn2+(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF. | Sigismundite | (Ba◻)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | Dickinsonite-(KMnNa) | (KNa)(Mn2+◻)Ca(Na2Na)Mn2+13Al(PO4)11(PO4)(OH)2 |
| 8.BF.05 | Arrojadite-(KNa) | (KNa)(NaNa)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | Fluorarrojadite-(BaNa) | (Ba◻)(NaNa)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)F2 |
| 8.BF.05 | Arrojadite-(KFe) | (KNa)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | Arrojadite-(PbFe) | (Pb◻)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | Fluorarrojadite-(BaFe) | (Ba◻)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)F2 |
| 8.BF.05 | 'Unnamed (Ba-dominant member of dickinsonite group)' | |
| 8.BF.05 | 'Unnamed (Pb-dominant member of dickinsonite group)' | |
| 8.BF.05 | Arrojadite-(SrFe) | (Sr◻)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | 'Arrojadite-(NaFe)' | (NaNa)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | Arrojadite-(BaNa) | (Ba◻)(NaNa)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | 'Arrojadite-(KFeNa)' | (KNa)(Fe2+◻)Ca(Na2Na)Fe2+13Al(PO4)11(PO4)(OH)2 |
| 8.BF.05 | 'Ferri-arrojadite-(BaNa)' | (Ba◻)(NaNa)Ca(Na2◻)Fe2+13Fe3+(PO4)11(PO3OH)(OH)2 |
| 8.BF.05 | 'Fluorarrojadite-(KNa)' | (KNa)(NaNa)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)F2 |
| 8.BF.05 | 'Fluorarrojadite-(NaFe)' | (NaNa)(Fe2+◻)Ca(Na2◻)Fe2+13Al(PO4)11(PO3OH)F2 |
| 8.BF.05 | Fluorcarmoite-(BaNa) | (Ba◻)(NaNa)Ca(Na2◻)Mg13Al(PO4)11(PO3OH)F2 |
| 8.BF.10 | Samuelsonite | (Ca,Ba)Ca8Fe2+2Mn2+2Al2(PO4)10(OH)2 |
| 8.BF.15 | Griphite | Na4Li2Ca6(Mn2+,Fe2+,Mg)19Al8(PO4)24(F,OH)8 |
| 8.BF.20 | Nabiasite | BaMn9(VO4)6(OH)2 |
| 8.BF.25 | Starovaite | KCu5O(VO4)3 |
| 8.BF.35 | Cryptochalcite | K2Cu5O(SO4)5 |
| 8.BF.35 | Cesiodymite | CsKCu5O(SO4)5 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 10.4437% | 3,238 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
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 Achyrophanite
mindat.org URL:
https://www.mindat.org/min-52919.html
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References for Achyrophanite
Reference List:
Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2018) CNMNC Newsletter No 43, New minerals and nomenclature modifications approved in 2018. Mineralogical Magazine, 82 (3) 779-785 doi:10.1180/mgm.2018.72p.783
Pekov, Igor V.; Zubkova, Natalia V.; Koshlyakova, Natalia N.; Belakovskiy, Dmitry I.; Vigasina, Marina F.; Agakhanov, Atali A.; Britvin, Sergey N.; Turchkova, Anna G.; Sidorov, Evgeny G.; Zhegunov, Pavel S.; et al. (2025) Achyrophanite, (K,Na)3(Fe3+,Ti,Al,Mg)5O2(AsO4)5, a New Mineral with the Novel Structure Type from Fumarolic Exhalations of the Tolbachik Volcano, Kamchatka, Russia. Minerals, 15 (7). doi:10.3390/min15070706
Localities for Achyrophanite
Showing 1 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.
Russia (TL) | |
| Hålenius et al. (2018) +2 other references |
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Arsenatnaya fumarole, Second scoria cone, Northern Breakthrough, Great Fissure eruption, Tolbachik Volcanic field, Milkovsky District, Kamchatka Krai, Russia