Ashcroftine-(Y)
A valid IMA mineral species - grandfathered
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About Ashcroftine-(Y)
Frederick Noel Ashcroft
Formula:
K5Na5(Y,Ca)12Si28O70(OH)2(CO3)8 · 8H2O
Colour:
Pink
Lustre:
Sub-Vitreous, Waxy, Silky
Hardness:
5
Specific Gravity:
2.61
Crystal System:
Tetragonal
Name:
Named by Max Hutchinson Hey and Frederick Allen Bannister in honor of Frederick Noel Ashcroft [August 28, 1878 Wavertree, near Liverpool, United Kingdom - April 4, 1949 London, United Kingdom], well known British mineral collector.
Named as kalithomsonite in 1932 by S. G. Gordon, for its resemblance to thomsonite and its potassium content. Later Hey & Bannister (1933) showed that the mineral has no close relationship to thomsonite and gave it the name ashcroftine. The suffix was added in 1987 by the IMA to denote the dominant REE.
Named as kalithomsonite in 1932 by S. G. Gordon, for its resemblance to thomsonite and its potassium content. Later Hey & Bannister (1933) showed that the mineral has no close relationship to thomsonite and gave it the name ashcroftine. The suffix was added in 1987 by the IMA to denote the dominant REE.
Unique Identifiers
Mindat ID:
389
Long-form identifier:
mindat:1:1:389:0
Similar Names
| Ashcroftine-(Ce) | Valid as an unnamed mineral | K5Na5(Ce,Ca)12Si28O70(OH)2(CO3)8 · 8H2O |
IMA Classification of Ashcroftine-(Y)
Approved, 'Grandfathered' (first described prior to 1959)
IMA status notes:
Renamed by the IMA
IMA Formula:
K5Na5Y12Si28O70(OH)2(CO3)8·8H2O
Classification of Ashcroftine-(Y)
9.DN.15
9 : SILICATES (Germanates)
D : Inosilicates
N : Inosilicates with 6-periodic double chains
9 : SILICATES (Germanates)
D : Inosilicates
N : Inosilicates with 6-periodic double chains
70.3.1.1
70 : INOSILICATES Column or Tube Structures
3 : Column or Tube Structures with balo-silicates
70 : INOSILICATES Column or Tube Structures
3 : Column or Tube Structures with balo-silicates
14.8.9
14 : Silicates not Containing Aluminum
8 : Silicates of Group III metals other than Al
14 : Silicates not Containing Aluminum
8 : Silicates of Group III metals other than Al
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 |
|---|---|---|
| Acf-Y | 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 Ashcroftine-(Y)
Sub-Vitreous, Waxy, Silky
Transparency:
Transparent
Colour:
Pink
Streak:
White
Hardness:
5 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
{100}, also {001} good
{100}, also {001} good
Fracture:
Irregular/Uneven
Density:
2.61 g/cm3 (Measured) 2.60 g/cm3 (Calculated)
Optical Data of Ashcroftine-(Y)
Type:
Uniaxial (+)
RI values:
nω = 1.536 - 1.537 nε = 1.545 - 1.549
Birefringence:
0.010
Max. Birefringence:
δ = 0.009 - 0.012
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:
None to Very Low
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.
Optical Extinction:
Parallel
Pleochroism:
Non-pleochroic
Chemistry of Ashcroftine-(Y)
Mindat Formula:
K5Na5(Y,Ca)12Si28O70(OH)2(CO3)8 · 8H2O
Element Weights:
Crystallography of Ashcroftine-(Y)
Crystal System:
Tetragonal
Class (H-M):
4/mmm(4/m2/m2/m) - Ditetragonal Dipyramidal
Space Group:
I4/mmm
Cell Parameters:
a = 23.99 Å, c = 17.51 Å
Ratio:
a:c = 1 : 0.73
Unit Cell V:
10,077.36 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Acicular, rod-like
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0001130 | Ashcroftine-(Y) | Moore P B, Sen Gupta P K, Schlemper E O, Merlino S (1987) Ashcroftine, ca. K10Na10(Y,Ca)24(OH)4(CO3)16(Si56O140).16H2O, a structure with enormous polyanions American Mineralogist 72 1176-1189 |  | 1987 | 0 | 293 | |
| 0001129 | Ashcroftine-(Y) | Moore P B, Sen Gupta P K, Schlemper E O, Merlino S (1987) Ashcroftine, ca. K10Na10(Y,Ca)24(OH)4(CO3)16(Si56O140).16H2O, a structure with enormous polyanions American Mineralogist 72 1176-1189 | | 1987 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 17.00 Å | (100) |
| 12.0 Å | (90) |
| 7.62 Å | (60) |
| 7.10 Å | (20) |
| 6.01 Å | (30) |
| 5.38 Å | (30) |
| 3.11 Å | (50) |
| 2.69 Å | (50) |
Comments:
22-508
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Ashcroftine-(Y)
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1924,867.
University of Copenhagen, Copenhagen, Denmark.
Harvard University, Cambridge, Massachusetts, USA, 110266.
National Museum of Natural History, Washington, D.C., USA, 95320, R4333.
University of Copenhagen, Copenhagen, Denmark.
Harvard University, Cambridge, Massachusetts, USA, 110266.
National Museum of Natural History, Washington, D.C., USA, 95320, R4333.
Synonyms of Ashcroftine-(Y)
Other Language Names for Ashcroftine-(Y)
Dutch:Ashcroftine-(Y)
French:Ashcroftine-(Y)
German:Ashcroftin-(Y)
Norwegian:Ashcroftin-(Y)
Russian:Ашкрофтин
Common Associates
Associations Based on Photo Data:
| 8 photos of Ashcroftine-(Y) associated with Calcite | CaCO3 |
| 3 photos of Ashcroftine-(Y) associated with Fluorite | CaF2 |
| 3 photos of Ashcroftine-(Y) associated with Aegirine | NaFe3+Si2O6 |
| 3 photos of Ashcroftine-(Y) associated with Elpidite | Na2ZrSi6O15 · 3H2O |
| 2 photos of Ashcroftine-(Y) associated with Polylithionite | KLi2Al(Si4O10)(F,OH)2 |
| 1 photo of Ashcroftine-(Y) associated with Graphite | C |
Related Minerals - Strunz-mindat Grouping
| 9.DN. | Letnikovite-(Ce) | (Na◻)Ca2Ce2[Si7O17(OH)]F4(H2O)4 |
| 9.DN.05 | Zektzerite | LiNaZrSi6O15 |
| 9.DN.05 | Emeleusite | Li2Na4Fe2Si12O30 |
| 9.DN.05 | Tuhualite | NaFe2+Fe3+Si6O15 |
| 9.DN.10 | Semenovite-(Ce) | Na8Ca2FeBe6Ce2Si14O40(OH)4F4 |
| 9.DN.15 | 'Ashcroftine-(Ce)' | K5Na5(Ce,Ca)12Si28O70(OH)2(CO3)8 · 8H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 4.9594% | 1,537 | 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 Ashcroftine-(Y)
Not fluorescent.
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 Ashcroftine-(Y)
mindat.org URL:
https://www.mindat.org/min-389.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Ashcroftine-(Y)
Reference List:
Hey, Max H., Bannister, F. A. (1933) Studies on the zeolites. Part IV. Ashcroftine (kalithomsonite of S. G. Gordon) Mineralogical Magazine and Journal of the Mineralogical Society, 23 (140) 305-308 doi:10.1180/minmag.1933.023.140.02
Moore, P. B., Bennett, J. M., Louisnathan, S. J. (1969) Ashcroftine is not a zeolite!. Mineralogical Magazine, 37 (288) 515-517 doi:10.1180/minmag.1969.037.288.12
Fleischer, M.; Nickel, E.H. (1970) New Minerals Names. American Mineralogist, 55 (9-10). p.1810-1818.
Nickel, Ernest H., Mandarino, Joseph A. (1987) Procedures involving the IMA Commission on New Minerals and Mineral Names and guidelines on mineral nomenclature. American Mineralogist, 72 (9-10) 1031-1042
Moore, Paul Brian, Gupta, Pradip K Sen, Schlemper, Elmer O., Merlino, Stefano (1987) Ashcroftine, ca. K10Na10(Y,Ca)24(OH)4(CO3)16(Si56O140)·16H2O, a structure with enormous polyanions. American Mineralogist, 72 (11-12) 1176-1189
Krivovichev, Sergey V.; Yakovenchuk, Victor N.; Goychuk, Olga F.; Kasatkin, Anatoly V.; Pakhomovsky, Yakov A.; Agakhanov, Atali A.; Chernyavsky, Alexey V. (2026) Silicate Nanotubules in the Crystal Structure of K6(Na4Ca)(Y8Ca3Mn)[Si28O68(OH)2](CO3)8F2·9H2O, a Mineral Phase from the Khibiny Alkaline Massif (Kola Peninsula, Russia), and the Problem of Ashcroftine-(Y). Minerals, 16 (5). doi:10.3390/min16050492
Localities for Ashcroftine-(Y)
Showing 4 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.
Canada | |
| Grice (1989) +1 other reference |
Greenland (TL) | |
| Nature (1932) +2 other references |
Italy | |
| Anthony et al. (1995, reprinted 2003) +1 other reference |
Russia | |
| Krivovichev et al. (2026) |
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Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Montérégie, Québec, Canada