Grayite
A valid IMA mineral species - grandfathered
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About Grayite
Formula:
(Th,Pb,Ca)(PO4) · H2O
Colour:
Dark reddish brown, rarely tannish yellow
Lustre:
Resinous, Waxy, Greasy
Specific Gravity:
6.41 (Calculated)
Crystal System:
Hexagonal
Member of:
Name:
Named in honor of Anton Gray, chief geologist, Kennecott Copper Corporation and advisor to the United Kingdom Atomic Energy Authority.
Type Locality:
Isostructural with:
Originally powdery or cryptocrystalline. Rarely in subhedral resinous crystals.
Possibly identical to brockite? See also the dubious smirnovskite.
Compare 'UM1979-08-PO:CCaFeHREESiTh'; 'UM1980-04-PO:CaHREETh', 'UM1979-07-PO:CaFeHREESiTh'.
Possibly identical to brockite? See also the dubious smirnovskite.
Compare 'UM1979-08-PO:CCaFeHREESiTh'; 'UM1980-04-PO:CaHREETh', 'UM1979-07-PO:CaFeHREESiTh'.
Unique Identifiers
Mindat ID:
1743
Long-form identifier:
mindat:1:1:1743:1
Similar Names
IMA Classification of Grayite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
(Th3+,Pb2+,Ca)(PO4)·H2O
First published:
1957
Classification of Grayite
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
40.4.7.4
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
19.10.8
19 : Phosphates
10 : Phosphates of Pb, Th, V and Bi
19 : Phosphates
10 : Phosphates of Pb, Th, V and Bi
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 |
|---|---|---|
| Gry | 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 Grayite
Resinous, Waxy, Greasy
Transparency:
Translucent
Colour:
Dark reddish brown, rarely tannish yellow
Fracture:
Conchoidal
Density:
6.41 g/cm3 (Calculated)
Optical Data of Grayite
Type:
Uniaxial
RI values:
nω = 1.66 nε = 1.69
Birefringence:
moderate (~0.03)
Max. Birefringence:
δ = 0.030
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.
Chemistry of Grayite
Mindat Formula:
(Th,Pb,Ca)(PO4) · H2O
Element Weights:
Crystallography of Grayite
Crystal System:
Hexagonal
Class (H-M):
622 - Trapezohedral
Space Group:
P6222
Cell Parameters:
a = 6.957 Å, c = 6.396 Å
Ratio:
a:c = 1 : 0.919
Unit Cell V:
268.09 ų (Calculated from Unit Cell)
Z:
3
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.05 Å | (20) |
| 4.35 Å | (50) |
| 3.46 Å | (10) |
| 3.03 Å | (100) |
| 2.82 Å | (80) |
| 2.36 Å | (10) |
| 2.15 Å | (80) |
| 1.856 Å | (50) |
Comments:
42-1389
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47) | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 34 : Complex granite pegmatites |
Geological Setting:
Has been found in granite pegmatite (Maine).
Type Occurrence of Grayite
Geological Setting of Type Material:
Originally in a lithia-rich granite pegmatite.
Other Language Names for Grayite
Relationship of Grayite to other Species
Member of:
Other Members of Rhabdophane Group:
| Brockite | (Ca,Th,Ce)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 |
| Tristramite | (Ca,U4+,Fe3+)(PO4,SO4) · 2H2O | Hex. 622 : P6222 |
| 'UM1993-07-PO:CaCeHLa' | (Ca,Ce,La,REE)PO4 · nH2O | Hex. 622 : P6222 |
Common Associates
Associations Based on Photo Data:
| 2 photos of Grayite associated with Xenotime-(Y) | Y(PO4) |
| 1 photo of Grayite associated with Albite | Na(AlSi3O8) |
| 1 photo of Grayite associated with Allanite Group | (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) |
| 1 photo of Grayite associated with 'Thorogummite' | (Th,U)(SiO4)1-x(OH)4x |
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 | Tristramite | (Ca,U4+,Fe3+)(PO4,SO4) · 2H2O |
| 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 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 67.2526% | 2,690,104 | 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: –
| 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
Fluorescence of Grayite
Specimens from Havey #2 Quarry, Topsham, Maine fluoresce yellow in SW UV.
Other Information
Thermal Behaviour:
Grayite may give a monazite-like powder pattern after heating to 850 degrees C.
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 Grayite
mindat.org URL:
https://www.mindat.org/min-1743.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Grayite
Reference List:
Localities for Grayite
Showing 21 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.
Australia | |
| Bottrill et al. (2024) |
Austria | |
| Auer (2026) |
Bulgaria | |
| Zidarov et al. (2011) | |
Germany | |
| Witzke (2011) |
Japan | |
| Terada et al (1994) |
Namibia | |
| Joan Rosell - rosellminerals.com |
Poland | |
| Kucha et al. (1980) +1 other reference |
Uganda | |
| Gallagher (1967) |
USA | |
| Eckel et al. (1997) |
| Eckel et al. (1997) |
| Rudy Bolona |
| Specimen in collection of Andrew Kruegel |
| Fred Davis - ... |
| King et al. (1994) |
| Buchholz et al. (2014) |
| Buchholz et al. (2013) |
| Foord et al. (1999) |
| Buchholz (2002) +1 other reference |
| Cordura |
Zimbabwe (TL) | |
| - (1962) +1 other reference |
| Bowie |
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Brabant Farm 168, Karibib Constituency, Erongo Region, Namibia