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Eylettersite
A valid IMA mineral species
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About Eylettersite
Lea Eyletters and L. Van Wambeke
Formula:
Th0.75Al3(PO4)2(OH)6
The type material contains minor Pb replacing Th, and minor Si replacing P.
Colour:
Cream white
Lustre:
Vitreous
Hardness:
3 - 4
Specific Gravity:
3.34 - 3.38
Crystal System:
Trigonal
Member of:
Name:
Named in 1972 by L. Van Wambeke after his wife, Lea Eyletters.
Type Locality:
This page provides mineralogical data about Eylettersite.
Unique Identifiers
Mindat ID:
1430
Long-form identifier:
mindat:1:1:1430:0
IMA Classification of Eylettersite
Approved
IMA Formula:
Th4+0.75Al3(PO4)2(OH)6
Approval year:
1969
First published:
1972
Classification of Eylettersite
8.BL.10
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
L : With medium-sized and large cations, (OH, etc.):RO4 = 3:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
L : With medium-sized and large cations, (OH, etc.):RO4 = 3:1
41.5.12.2
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
5 : (AB)2(XO4)Zq
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
5 : (AB)2(XO4)Zq
17.6.17
17 : Silicates Containing other Anions
6 : Silicates with phosphate
17 : Silicates Containing other Anions
6 : Silicates with phosphate
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 |
|---|---|---|
| Eyl | 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 Eylettersite
Vitreous
Transparency:
Transparent
Colour:
Cream white
Streak:
White
Hardness:
3 - 4 on Mohs scale
Density:
3.34 - 3.38 g/cm3 (Measured) 3.47(3) g/cm3 (Calculated)
Optical Data of Eylettersite
Type:
Uniaxial (-)
RI values:
nε = 1.615 - 1.66
Surface Relief:
Unknown
Chemistry of Eylettersite
Mindat Formula:
Th0.75Al3(PO4)2(OH)6
The type material contains minor Pb replacing Th, and minor Si replacing P.
The type material contains minor Pb replacing Th, and minor Si replacing P.
Element Weights:
Crystallography of Eylettersite
Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R3m
Cell Parameters:
a = 6.99 Å, c = 16.68(2) Å
Ratio:
a:c = 1 : 2.386
Unit Cell V:
705.80 ų (Calculated from Unit Cell)
Z:
3
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.95 Å | (100) |
| 3.51 Å | (60) |
| 5.70 Å | (55) |
| 2.187 Å | (40) |
| 1.899 Å | (30) |
| 1.748 Å | (20) |
| 2.848 Å | (15) |
Comments:
Kobokobo pegmatite, Congo. Data from the type description.
Type Occurrence of Eylettersite
General Appearance of Type Material:
pulverant
Place of Conservation of Type Material:
Euratom, Ispra, Italy
National Museum of Natural History, Washington, D.C.,
USA, 136443
National Museum of Natural History, Washington, D.C.,
USA, 136443
Geological Setting of Type Material:
alteration product of thorian crandallite in a phosphate-rich granite
Associated Minerals at Type Locality:
Synonyms of Eylettersite
Other Language Names for Eylettersite
Relationship of Eylettersite to other Species
Member of:
Other Members of Plumbogummite Group:
| Arsenobenauite | SrFe3+3(AsO4)(AsO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| Benauite | SrFe3+3(PO4)(PO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| Crandallite | CaAl3(PO4)(PO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| Florencite-(Ce) | CeAl3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
| Florencite-(La) | LaAl3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
| Florencite-(Nd) | NdAl3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
| Florencite-(Sm) | SmAl3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
| Galloplumbogummite | Pb(Ga,Al,Ge)3(PO4)2(OH)6 | Trig. 3m : R3m |
| Gorceixite | BaAl3(PO4)(PO3OH)(OH)6 | Mon. m : Bm |
| Goyazite | SrAl3(PO4)(PO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| Kintoreite | PbFe3(PO4)(PO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| 'Kintoreite-2c' | PbFe3+3(PO4)2(OH,H2O)6 | |
| Plumbogummite | PbAl3(PO4)(PO3OH)(OH)6 | Trig. 3m(32/m) : R3m |
| Springcreekite | BaV3+3(PO4)2(OH,H2O)6 | Trig. 3m(32/m) : R3m |
| 'UM2006-23-PO:AlBiCaFeH' | (Ca,Bi)(Fe,Al)3(PO4)(PO3OH)(OH)6 | |
| 'Unnamed (As-analogue of Zaïrite)' | (Bi,Pb)Fe3+3(AsO4)2(OH)6 | |
| Waylandite | BiAl3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
| Zaïrite | BiFe3+3(PO4)2(OH)6 | Trig. 3m(32/m) : R3m |
Common Associates
Associations Based on Photo Data:
| 2 photos of Eylettersite associated with Mundite | Al(UO2)3(PO4)2(OH)3 · 5.5H2O |
| 2 photos of Eylettersite associated with Threadgoldite | Al(UO2)2(PO4)2(OH) · 8H2O |
| 2 photos of Eylettersite associated with Phuralumite | Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 |
| 1 photo of Eylettersite associated with Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
| 1 photo of Eylettersite associated with Microcline | K(AlSi3O8) |
| 1 photo of Eylettersite associated with Quartz | SiO2 |
Related Minerals - Strunz-mindat Grouping
| 8.BL. | Kiryuite | NaMnAl(PO4)F3 |
| 8.BL. | Metaheimite | PbCu2(AsO4)(OH)3 |
| 8.BL. | Graulichite-(La) | LaFe3+3(AsO4)2(OH)6 |
| 8.BL. | Cloudite | BaFe3+3(PO4)(SO4)(OH)6 |
| 8.BL. | Oberwolfachite | SrFe3+3(AsO4)(SO4)(OH)6 |
| 8.BL. | Arsenobenauite | SrFe3+3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.05 | Gallobeudantite | PbGa3(AsO4)(SO4)(OH)6 |
| 8.BL.05 | Slottaite | SrFe3+3(PO4)(SO4)(OH)6 |
| 8.BL.05 | Corkite | PbFe3+3(PO4)(SO4)(OH)6 |
| 8.BL.05 | Hidalgoite | PbAl3(AsO4)(SO4)(OH)6 |
| 8.BL.05 | Hinsdalite | PbAl3(PO4)(SO4)(OH)6 |
| 8.BL.05 | 'UM2011-07-POSO:AlBaH' | BaAl3(PO4)(SO4)(OH)6 |
| 8.BL.05 | Kemmlitzite | SrAl3(AsO4)(SO4)(OH)6 |
| 8.BL.05 | Beudantite | PbFe3+3(AsO4)(SO4)(OH)6 |
| 8.BL.05 | Weilerite | BaAl3(AsO4)(SO4)(OH)6 |
| 8.BL.05 | Woodhouseite | CaAl3(PO4)(SO4)(OH)6 |
| 8.BL.05 | Svanbergite | SrAl3(PO4)(SO4)(OH)6 |
| 8.BL.10 | Segnitite | PbFe3+3AsO4(AsO3OH)(OH)6 |
| 8.BL.10 | Arsenogoyazite | SrAl3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.10 | Arsenogorceixite | BaAl3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.10 | Dussertite | BaFe3+3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.10 | Galloplumbogummite | Pb(Ga,Al,Ge)3(PO4)2(OH)6 |
| 8.BL.10 | Stibiosegnitite | Pb(Fe3+2.5Sb5+0.5)(AsO4)2(OH)6 |
| 8.BL.10 va | 'Viséite' | |
| 8.BL.10 | Arsenocrandallite | CaAl3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.10 | Benauite | SrFe3+3(PO4)(PO3OH)(OH)6 |
| 8.BL.10 | Philipsbornite | PbAl3(AsO4)(AsO3OH)(OH)6 |
| 8.BL.10 | Crandallite | CaAl3(PO4)(PO3OH)(OH)6 |
| 8.BL.10 | Springcreekite | BaV3+3(PO4)2(OH,H2O)6 |
| 8.BL.10 | Kintoreite | PbFe3(PO4)(PO3OH)(OH)6 |
| 8.BL.10 | Plumbogummite | PbAl3(PO4)(PO3OH)(OH)6 |
| 8.BL.10 | Gorceixite | BaAl3(PO4)(PO3OH)(OH)6 |
| 8.BL.10 | Goyazite | SrAl3(PO4)(PO3OH)(OH)6 |
| 8.BL.13 | Florencite-(Ce) | CeAl3(PO4)2(OH)6 |
| 8.BL.13 | Florencite-(La) | LaAl3(PO4)2(OH)6 |
| 8.BL.13 | Florencite-(Nd) | NdAl3(PO4)2(OH)6 |
| 8.BL.13 | Zaïrite | BiFe3+3(PO4)2(OH)6 |
| 8.BL.13 | Arsenoflorencite-(La) | LaAl3(AsO4)2(OH)6 |
| 8.BL.13 | 'Arsenoflorencite-(Nd)' | NdAl3(AsO4)2(OH)6 |
| 8.BL.13 | 'Unnamed (As-analogue of Zaïrite)' | (Bi,Pb)Fe3+3(AsO4)2(OH)6 |
| 8.BL.13 | Arsenoflorencite-(Ce) | CeAl3(AsO4)2(OH)6 |
| 8.BL.13 | Graulichite-(Ce) | CeFe3+3(AsO4)2(OH)6 |
| 8.BL.13 | 'Arsenowaylandite' | BiAl3(AsO4)2(OH)6 |
| 8.BL.13 | Waylandite | BiAl3(PO4)2(OH)6 |
| 8.BL.13 | Florencite-(Sm) | SmAl3(PO4)2(OH)6 |
| 8.BL.15 | Viitaniemiite | Na(Ca,Mn2+)Al(PO4)(F,OH)3 |
| 8.BL.25 | Pattersonite | PbFe3+3(PO4)2(OH)5 · H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 31.8174% | 1,272,696 | 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
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 Eylettersite
mindat.org URL:
https://www.mindat.org/min-1430.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
Kobokobo pegmatite, Mwenga Territory, South Kivu, DR Congo