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Triangulite

A valid IMA mineral species
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09378150017271927132985.jpg
Triangulite, etc.

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
04229230017271927169584.jpg
Triangulite

Rhyolite Ridge Li-B Deposit, Esmeralda County, Nevada, USA
02788940017271927241793.jpg
Triangulite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
09378150017271927132985.jpg
Triangulite, etc.

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
04229230017271927169584.jpg
Triangulite

Rhyolite Ridge Li-B Deposit, Esmeralda County, Nevada, USA
02788940017271927241793.jpg
Triangulite

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
09378150017271927132985.jpg
Triangulite, etc.

Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
04229230017271927169584.jpg
Triangulite

Rhyolite Ridge Li-B Deposit, Esmeralda County, Nevada, USA
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About TrianguliteHide

Formula:
Al3(UO2)4(PO4)4(OH)5 · 5H2O
Colour:
Bright yellow, yellow-green
Lustre:
Vitreous
Hardness:
2 - 3
Specific Gravity:
3.7
Crystal System:
Triclinic
Name:
Named for the triangular habit of its crystals.
Ranunculite-Triangulite Group


Unique IdentifiersHide

Mindat ID:
4014
Long-form identifier:
mindat:1:1:4014:9

IMA Classification of TrianguliteHide

Classification of TrianguliteHide

Strunz-mindat (2026):
8.EB.45

8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
Dana 8th ed.:
40.2a.34.1

40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
2a : AB2(XO4)2·xH2O, containing (UO2)2+
Hey's CIM Ref.:
19.11.24

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

Pronunciation of TrianguliteHide

Pronunciation:
PlayRecorded byCountry
Jolyon RalphUnited Kingdom

Physical Properties of TrianguliteHide

Lustre:
Vitreous
Transparency:
Transparent
Colour:
Bright yellow, yellow-green
Hardness:
2 - 3 on Mohs scale
Density:
3.7 g/cm3 (Measured)    3.68 g/cm3 (Calculated)

Optical Data of TrianguliteHide

Type:
Biaxial (+)
RI values:
nα = 1.639 nβ = 1.665(2) nγ = 1.704(2)
2V:
Measured: 80° , Calculated: 82°
Max. Birefringence:
δ = 0.065
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:
relatively weak
Pleochroism:
Visible
Comments:
Y pale green-yellow, Z bright yellow.
Comments:
Z ≃ [011], Y ≃ [011], X ⊥ [100]

Chemistry of TrianguliteHide

Mindat Formula:
Al3(UO2)4(PO4)4(OH)5 · 5H2O
Element Weights:
Element% weight
U55.483 %
O31.699 %
P7.220 %
Al4.717 %
H0.881 %

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 TrianguliteHide

Crystal System:
Triclinic
Cell Parameters:
a = 10.39(3) Å, b = 10.56(3) Å, c = 10.60(3) Å
α = 116.4(1)°, β = 107.8(1)°, γ = 113.4(1)°
Ratio:
a:b:c = 0.984 : 1 : 1.004
Unit Cell V:
774.22 ų (Calculated from Unit Cell)
Z:
1
Morphology:
Triangular tablets flattened on {100} or pseudo rhombohedral crystals.
Twinning:
Common, 180° rotational twin about [011] and [011].
Comment:
Point Group: 1 or 1; Space Group: P1 or P1.

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
7.80 Å(100)
4.70 Å(30)
3.87 Å(80)
3.74 Å(20)
3.63 Å(20)
3.39 Å(20)
3.15 Å(70)
2.99 Å(50)
2.86 Å(20)
2.574 Å(20)

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 TrianguliteHide

Type Locality:
ⓘ Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo
General Appearance of Type Material:
Bright yellow, aggregates of flat, triangular or rhombohedral crystals with a maximum length of 0.2 mm.
Place of Conservation of Type Material:
Royal Museum of Central Africa in Tervuren, Belgium, RMG6192.
Geological Setting of Type Material:
Quartz-K-feldspar-columbite zone of a complex pegmatite.
Associated Minerals at Type Locality:
BerylMeta-autunitePhosphuranyliteRanunculiteZircon
Reference:
Deliens, Michel, Piret, Paul (1982) Les phosphates d'uranyle et d'aluminium de Kobokobo. VI. La triangulite, Al3(UO2•PO4)4(OH)5•5H2O, nouveau minéral. Bulletin de Minéralogie, 105 (6) 611-614 doi:10.3406/bulmi.1982.7642

Synonyms of TrianguliteHide

Other Language Names for TrianguliteHide

German:Triangulit
Simplified Chinese:磷铝铀矿 V
Spanish:Triangulita

Common AssociatesHide

Associations Based on Photo Data:
2 photos of Triangulite associated with FurongiteAl13(UO2)7(PO4)13(OH)14 · 58H2O
2 photos of Triangulite associated with KobokoboiteAl6(PO4)4(OH)6 · 11H2O
1 photo of Triangulite associated with UraniniteUO2

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.40RanunculiteHAl(UO2)(PO4)(OH)3 · 4H2OMon. 2/m : B2/b
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) 55.4828% 13,870,700 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 TrianguliteHide

In UV light:
Type material was not fluorescent. Material from Rhyolite Ridge, Nevada is fluorescent bright green under SW UV.

Other InformationHide

Notes:
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 TrianguliteHide

References for TrianguliteHide

Localities for TrianguliteHide

Showing 3 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.
DR Congo (TL)
 
  • South Kivu
    • Mwenga Territory
Deliens et al. (1982)
Spain
 
  • Extremadura
    • Cáceres
      • Tejeda de Tiétar
www.foro-minerales.com (n.d.)
USA
 
  • Nevada
    • Esmeralda County
Castor et al. (2004)
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