Tristramite
A valid IMA mineral species
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About Tristramite
Sir Tristram, King of Lyonesse
Formula:
(Ca,U4+,Fe3+)(PO4,SO4) · 2H2O
Colour:
Light yellow, greenish-yellow
Lustre:
Vitreous
Hardness:
3 - 4
Specific Gravity:
3.8 - 4.2
Crystal System:
Hexagonal
Member of:
Name:
Named after Tristram, a medieval figure of the Arthurian legend and a possible resident of the discovery area.
Unique Identifiers
Mindat ID:
4025
Long-form identifier:
mindat:1:1:4025:5
IMA Classification of Tristramite
Approved
IMA Formula:
(Ca,U4+,Fe3+)(PO4,S6+O4)·2H2O
Approval year:
1982
First published:
1983
Classification of Tristramite
8.CJ.45
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
J : With only large cations
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
J : With only large cations
40.4.7.6
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
4 : (AB)5(XO4)2·xH2O
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
4 : (AB)5(XO4)2·xH2O
22.3.22
22 : Phosphates, Arsenates or Vanadates with other Anions
3 : Phosphates, arsenates or vanadates with sulphates
22 : Phosphates, Arsenates or Vanadates with other Anions
3 : Phosphates, arsenates or vanadates with sulphates
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 |
|---|---|---|
| Ttm | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Tristramite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Tristramite
Vitreous
Transparency:
Translucent
Colour:
Light yellow, greenish-yellow
Hardness:
3 - 4 on Mohs scale
Cleavage:
None Observed
Density:
3.8 - 4.2 g/cm3 (Measured) 4.18 g/cm3 (Calculated)
Optical Data of Tristramite
Type:
Uniaxial (+)
RI values:
nω = 1.644(2) nε = 1.664(2)
Max. Birefringence:
δ = 0.020
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:
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:
Not Visible
Comments:
Under crossed polars there is a tendency to show an anomalous blue birefringence colour.
Chemistry of Tristramite
Mindat Formula:
(Ca,U4+,Fe3+)(PO4,SO4) · 2H2O
Element Weights:
Crystallography of Tristramite
Crystal System:
Hexagonal
Class (H-M):
622 - Trapezohedral
Space Group:
P6222
Cell Parameters:
a = 6.913(6) Å, c = 6.422(6) Å
Ratio:
a:c = 1 : 0.929
Unit Cell V:
265.79 ų (Calculated from Unit Cell)
Z:
3
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.99 Å | (100) |
| 2.83 Å | (100) |
| 2.14 Å | (50) |
| 1.850 Å | (50) |
| 5.99 Å | (40) |
| 4.37 Å | (40) |
| 3.46 Å | (30) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Type Occurrence of Tristramite
General Appearance of Type Material:
Fine-grained aggregates of acicular to fibrous crystals and as coarser-grained infillings occupying fine fractures and cavities.
Place of Conservation of Type Material:
1) Geochemistry and Petrology Division of the Institute of Geological Sciences
2) British Museum (Natural History), London, England
2) British Museum (Natural History), London, England
Geological Setting of Type Material:
Uraninite (var. pitchblende)-bearing quartz veins, with sulfides
Associated Minerals at Type Locality:
Synonyms of Tristramite
Other Language Names for Tristramite
Relationship of Tristramite to other Species
Member of:
Other Members of Rhabdophane Group:
| Brockite | (Ca,Th,Ce)PO4 · H2O | Hex. 622 : P6222 |
| Grayite | (Th,Pb,Ca)(PO4) · H2O | Hex. 622 : P6222 |
| Rhabdophane-(Ce) | Ce(PO4) · 0.6H2O | Trig. 32 : P3121 |
| Rhabdophane-(La) | La(PO4) · H2O | Hex. 622 : P6222 |
| Rhabdophane-(Nd) | Nd(PO4) · H2O | Hex. 622 : P6222 |
| Rhabdophane-(Y) | YPO4 · H2O | Hex. 622 : P6222 |
| 'UM1993-07-PO:CaCeHLa' | (Ca,Ce,La,REE)PO4 · nH2O | Hex. 622 : P6222 |
Related Minerals - Strunz-mindat Grouping
| 8.CJ. | Airdite | Sr(V4+O)2(PO4)2 · 4H2O |
| 8.CJ. | Dobšináite | Ca2Ca(AsO4)2 · 2H2O |
| 8.CJ. | Sainfeldite | Ca5(AsO4)2(AsO3OH)2 · 4H2O |
| 8.CJ. | Caesiumpharmacosiderite | CsFe3+4[(AsO4)3(OH)4] · 4H2O |
| 8.CJ. | Jeankempite | Ca5(AsO4)2(HAsO4)2 · 7H2O |
| 8.CJ.05 | Stercorite | (NH4)Na(PO3OH) · 4H2O |
| 8.CJ.10 | Swaknoite | (NH4)2Ca(PO3OH)2 · H2O |
| 8.CJ.10 | Mundrabillaite | (NH4)2Ca(PO3OH)2 · H2O |
| 8.CJ.15 | Nabaphite | NaBaPO4 · 9H2O |
| 8.CJ.15 | Nastrophite | Na(Sr,Ba)PO4 · 9H2O |
| 8.CJ.20 | Haidingerite | CaHAsO4 · H2O |
| 8.CJ.25 | Rhabdophane-(Y) | YPO4 · H2O |
| 8.CJ.25 | Vladimirite | Ca4(AsO4)2(AsO3OH) · 4H2O |
| 8.CJ.27 | 'Churchite-(Dy)' | (Dy,Sm,Gd,Nd)PO4 · 2H2O |
| 8.CJ.30 | Ferrarisite | Ca5(AsO4)2(HAsO4)2 · 9H2O |
| 8.CJ.35 | Fulbrightite | Ca(V4+O)2(As5+O4)2 · 4H2O |
| 8.CJ.35 | Machatschkiite | (Ca,Na)6(AsO4)(HAsO4)3(PO4,SO4) · 15H2O |
| 8.CJ.40 | Rauenthalite | Ca3(AsO4)2 · 10H2O |
| 8.CJ.40 | Phaunouxite | Ca3(AsO4)2 · 11H2O |
| 8.CJ.45 | Brockite | (Ca,Th,Ce)PO4 · H2O |
| 8.CJ.45 | Smirnovskite | (Th,Ca)PO4 · nH2O |
| 8.CJ.45 | Rhabdophane-(Ce) | Ce(PO4) · 0.6H2O |
| 8.CJ.45 | Rhabdophane-(La) | La(PO4) · H2O |
| 8.CJ.45 | Rhabdophane-(Nd) | Nd(PO4) · H2O |
| 8.CJ.45 | Grayite | (Th,Pb,Ca)(PO4) · H2O |
| 8.CJ.45 | Štěpite | U(AsO3OH)2 · 4H2O |
| 8.CJ.47 | Vysokýite | U4+[AsO2(OH)2]4 · 4H2O |
| 8.CJ.50 | Churchite-(Y) | Y(PO4) · 2H2O |
| 8.CJ.50 | Brushite | Ca(PO3OH) · 2H2O |
| 8.CJ.50 | Ardealite | Ca2(PO3OH)(SO4) · 4H2O |
| 8.CJ.50 | Pharmacolite | Ca(HAsO4) · 2H2O |
| 8.CJ.50 | 'Churchite-(Nd)' | Nd(PO4) · 2H2O |
| 8.CJ.55 | Mcnearite | NaCa5(AsO4)(HAsO4)4 · 4H2O |
| 8.CJ.60 | Dorfmanite | Na2(PO3OH) · 2H2O |
| 8.CJ.65 | Sincosite | Ca(V4+O)2(PO4)2 · 4H2O |
| 8.CJ.65 | Bariosincosite | Ba(V4+O)2(PO4)2 · 4H2O |
| 8.CJ.70 | Catalanoite | Na2(PO3OH) · 8H2O |
| 8.CJ.75 | Guérinite | Ca6(HAsO4)3(AsO4)2 · 10.5H2O |
| 8.CJ.85 | Ningyoite | (U,Ca,Ce)2(PO4)2 · 1-2H2O |
Fluorescence of Tristramite
Does not fluoresce in either short-wave or long-wave UV
Other Information
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 Tristramite
mindat.org URL:
https://www.mindat.org/min-4025.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Tristramite
Reference List:
Atkin, D., Basham, I. R., Bowles, J. F. W. (1983) Tristramite, a new calcium uranium phosphate of the rhabdophane group. Mineralogical Magazine, 47 (344) 393-396 doi:10.1180/minmag.1983.047.344.18
Localities for Tristramite
Showing 8 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.
China | |
| Guang Fan et al. (2013) |
Madagascar | |
| Berger et al. (2014) |
UK (TL) | |
| Atkin et al. (1983) |
| Atkin et al. (1983) | |
| Golley et al. (1995) |
| Bernard et al. (2004) |
| Golley et al. (1995) |
| Golley et al. (1995) |
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Wheal Trewavas, Rinsey, Breage, Cornwall, England, UK