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Ranunculite

A valid IMA mineral species
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03191950017271926088696.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
03390660017271926123200.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
05331560017271926158913.jpg
Ranunculite, etc.

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
03191950017271926088696.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
03390660017271926123200.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
05331560017271926158913.jpg
Ranunculite, etc.

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
03191950017271926088696.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
04243530017271926183605.jpg
Ranunculite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
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About RanunculiteHide

Formula:
HAl(UO2)(PO4)(OH)3 · 4H2O
Colour:
Golden Yellow
Lustre:
Waxy, Dull
Hardness:
3
Specific Gravity:
3.40
Crystal System:
Monoclinic
Name:
Named by Michel Deliens and Paul Piret in 1980 from the Latin ranunculus, buttercup, alluding to its gold-yellow color.
The structure of ranunculite is based upon infinite uranyl-phosphate sheets of novel topology. The two-dimensional representation of the structural unit consists of hexagons (occupied by U6+), pentagons (occupied by U6+), squares (occupied by Al3+) and triangles (occupied by P5+). Those sheets are stacked perpendicular to c; the interplanar distance is about 9.5 Å. They result from the clusters of edge-sharing uranyl hexagonal and pentagonal bipyramids linked by Al-octahedra and PO4 tetrahedra. The decoration of the sheets is unique but somewhat resembles the arrangement (of U-clusters, squares and triangles) observed in bijvoetite and lepersonnite topologies; the ring symbol is 6 1 5 1 4 2 3 2 . In the interlayer, there are two Al3+ -hosting sites (one [6]- and [5]-coordinated; the pyramidal one is only partially occupied), as well as isolated H2O groups. There is an extensive network of hydrogen bonds; adjacent sheets are either held by hydrogen bonds only or by tetramers of Al-polyhedra when occupied (through shared O19).


Unique IdentifiersHide

Mindat ID:
3365
Long-form identifier:
mindat:1:1:3365:3

IMA Classification of RanunculiteHide

Classification of RanunculiteHide

Strunz-mindat (2026):
8.EB.40

8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
Dana 8th ed.:
42.2.2.1

42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
2 : (AB)3(XO4)Zq·xH2O
Hey's CIM Ref.:
19.11.23

19 : Phosphates
11 : Phosphates of U

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

Physical Properties of RanunculiteHide

Lustre:
Waxy, Dull
Transparency:
Translucent
Colour:
Golden Yellow
Streak:
Pale yellow
Hardness:
3 on Mohs scale
Tenacity:
Brittle
Cleavage:
Imperfect/Fair
irregular, parallel to [100] and [001]
Density:
3.40 g/cm3 (Measured)    3.4042 g/cm3 (Calculated)

Optical Data of RanunculiteHide

Type:
Biaxial (-)
RI values:
nα = 1.643(2) nβ = 1.664(2) nγ = 1.670(2)
2V:
Measured: 56° , Calculated: 56°
Birefringence:
0.027
Max. Birefringence:
δ = 0.027
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:
very strong
Optical Extinction:
Oblique
Pleochroism:
Strong
Comments:
pale yellow to pale greenish yellow

Chemistry of RanunculiteHide

Mindat Formula:
HAl(UO2)(PO4)(OH)3 · 4H2O
Element Weights:
Element% weight
U46.123 %
O40.303 %
P6.002 %
Al5.228 %
H2.344 %

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

Crystallography of RanunculiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 11.1812(7) Å, b = 17.9281(5) Å, c = 17.91548(16) Å
β = 98.350(4)°
Ratio:
a:b:c = 0.624 : 1 : 0.999
Unit Cell V:
3,553.23 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Rounded nodules less than 1 mm, composed of many tiny plates. The plates are flattened on [010].
Comment:
three-dimensional electron diffraction (3D ED) techniques using a transmission electron microscope (TEM)

X-Ray Powder DiffractionHide

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 7: Great Oxidation Event<2.4
47a : [Near-surface hydration of prior minerals]
47c : [Carbonates, phosphates, borates, nitrates]
47f : [Uranyl (U⁶⁺) minerals]

Type Occurrence of RanunculiteHide

Type Locality:
ⓘ Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
General Appearance of Type Material:
Gold-yellow nodules, with mean diameter of 0.3 mm, rarely to 1 mm, and botryoidal crusts.
Place of Conservation of Type Material:
Royal Museum of Central Africa, Tervuren, Belgium, RGM 6201.
National Museum of Natural History, Washington, D.C., USA, 145686.

The ranunculite powder in the capillary used in this study has been registered as a structure type (paratype) in the Museum of Natural History in Luxembourg under the catalogue number PV038.
Geological Setting of Type Material:
Late stage mineralization in a granite pegmatite
Associated Minerals at Type Locality:
Meta-autuniteMoreauitePhosphuranylitePhuralumiteThreadgoldite
Upalite
Reference:
Dellens, Michel, Piret, Paul (1979) Ranunculite, AlH(UO2)(PO4)(OH)3 · 4H2O, a new mineral. Mineralogical Magazine, 43 (327) 321-323 doi:10.1180/minmag.1979.043.327.01

Synonyms of RanunculiteHide

Other Language Names for RanunculiteHide

German:Ranunculit
Simplified Chinese:磷铝铀矿 III
Spanish:Ranunculita

Common AssociatesHide

Associations Based on Photo Data:
1 photo of Ranunculite associated with 'Apatite'Ca5(PO4)3A
1 photo of Ranunculite associated with PhuralumiteAl2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9

Related Minerals - Strunz-mindat GroupingHide

8.EB.Meta-autunite GroupA1-2(UO2)2(TO4)2 · 5-10H2O
8.EB.05RauchiteNi(UO2)2(AsO4)2 · 10H2OTric. 1 : P1
8.EB.05UranocirciteBa(UO2)2(PO4)2 · 10H2OTet.
8.EB.05UranospiniteCa(UO2)2(AsO4)2 · 10H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.05ZeuneriteCu(UO2)2(AsO4)2 · 12H2OTet. 4/mmm(4/m2/m2/m) : I4/mmm
8.EB.05MetarauchiteNi(UO2)2(AsO4)2 · 8H2OTric. 1 : P1
8.EB.05HeinrichiteBa(UO2)2(AsO4)2 · 10H2OMon. 2/m : P2/b
8.EB.05KahleriteFe2+(UO2)2(AsO4)2 · 12H2OTet. 4/m : P42/n
8.EB.05HydronováčekiteMg(UO2)2(AsO4)2 · 12H2OTric. 1 : P1
8.EB.05TorberniteCu(UO2)2(PO4)2 · 12H2OTet. 4/mmm(4/m2/m2/m) : I4/mmm
8.EB.05NováčekiteMg(UO2)2(AsO4)2 · 10H2OMon. 2/m
8.EB.05AutuniteCa(UO2)2(PO4)2 · 10-12H2OOrth. mmm(2/m2/m2/m) : Pnma
8.EB.05SaléeiteMg(UO2)2(PO4)2 · 10H2OMon. 2/m
8.EB.05Xiangjiangite(Fe3+,Al)(UO2)4(PO4)2(SO4)2(OH) · 22H2OTet.
8.EB.10BassetiteFe2+(UO2)2(PO4)2 · 10H2OMon. 2/m
8.EB.10LehneriteMn2+(UO2)2(PO4)2 · 8H2OMon. 2/m
8.EB.10Meta-autuniteCa(UO2)2(PO4)2 · 6H2OTet. 4/mmm(4/m2/m2/m)
8.EB.10MetasaléeiteMg(UO2)2(PO4)2 · 8H2O
8.EB.10MetauranocirciteBa(UO2)2(PO4)2 · 7H2OMon. 2 : P21
8.EB.10MetauranospiniteCa(UO2)2(AsO4)2 · 8H2OTet. 4/m : P42/n
8.EB.10MetaheinrichiteBa(UO2)2(AsO4)2 · 8H2OMon. 2 : P21
8.EB.10MetakahleriteFe2+(UO2)2(AsO4)2 · 8H2OTric. 1 : P1
8.EB.10MetakirchheimeriteCo(UO2)2(AsO4)2 · 8H2OTric. 1 : P1
8.EB.10MetanováčekiteMg(UO2)2(AsO4)2 · 8H2OTet. 4/m : P4/n
8.EB.10MetanatroautuniteNa(UO2)(PO4)(H2O)3Tet. 4/mmm(4/m2/m2/m) : P4/ncc
8.EB.10MetatorberniteCu(UO2)2(PO4)2 · 8H2OTet. 4/m : P4/n
8.EB.10MetazeuneriteCu(UO2)2(AsO4)2 · 8H2OTet. 4/m : P42/n
8.EB.10PrzhevalskitePb2(UO2)3(PO4)2(OH)4 · 3H2OTet.
8.EB.10'Pseudo-autunite'(H3O)4Ca2(UO2)2(PO4)4 · 5H2OOrth.
8.EB.15AbernathyiteK(UO2)(AsO4) · 3H2OTet. 4/mmm(4/m2/m2/m) : P4/ncc
8.EB.15Uramphite(NH4)2(UO2)2(PO4)2 · 6H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.15Meta-ankoleiteK2(UO2)2(PO4)2 · 6H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.15NatrouranospiniteNa2(UO2)2(AsO4)2 · 5H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.15Trögerite(H3O)(UO2)(AsO4) · 3H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.15Chernikovite(H3O)2(UO2)2(PO4)2 · 6H2OTet. 4/mmm(4/m2/m2/m) : P4/nmm
8.EB.15Uramarsite(NH4)(UO2)(AsO4) · 3H2OTet. 4/mmm(4/m2/m2/m) : P4/mmm
8.EB.20ChistyakovaiteAl(UO2)2(AsO4)2(F,OH) · 6.5H2OMon.
8.EB.20ThreadgolditeAl(UO2)2(PO4)2(OH) · 8H2OMon.
8.EB.25Uranospathite(Al,◻)(UO2)2(PO4)2F · 20(H2O,F)Orth. mm2 : Pnn2
8.EB.25ArsenuranospathiteAl(UO2)2(AsO4)2F · 20H2OOrth. mm2 : Pnn2
8.EB.30Vochtenite(Fe2+,Mg)Fe3+(UO2)4(PO4)4(OH) · 12-13H2OMon.
8.EB.35CoconinoiteFe3+2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2OMon.
8.EB.45TrianguliteAl3(UO2)4(PO4)4(OH)5 · 5H2OTric.
8.EB.50FurongiteAl13(UO2)7(PO4)13(OH)14 · 58H2OTric. 1 : P1
8.EB.55ArsenosabugaliteH0.5Al0.5(UO2)2(AsO4)2 · 8H2OTric. 1 : P1
8.EB.55SabugaliteHAl(UO2)4(PO4)4 · 16H2OMon. 2/m : B2/m
8.EB.60Horákite(Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2] · 3.5H2OMon. 2/m : B2/b

RadioactivityHide

Radioactivity:
Element % Content Activity (Bq/kg) Radiation Type
Uranium (U) 46.1232% 11,530,800 α, β, γ
Thorium (Th) 0.0000% 0 α, β, γ
Potassium (K) 0.0000% 0 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: –

DistanceDose rateRisk
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

Fluorescence of RanunculiteHide

Other InformationHide

Notes:
Slowly soluble in 1:1 HNO3 and fairly soluble in hot 1:1 HCl.
radioactive
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 RanunculiteHide

References for RanunculiteHide

Localities for RanunculiteHide

Showing 2 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.
Hide all sections | Show all sections

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.
DR Congo (TL)
 
  • South Kivu
    • Mwenga Territory
Dellens et al. (1979) +1 other reference
Spain
 
  • Extremadura
    • Cáceres
      • Tejeda de Tiétar
www.foro-minerales.com (n.d.)
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