Eakerite
A valid IMA mineral species
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About Eakerite
Formula:
Ca2SnAl2Si6O18(OH)2 · 2H2O
Colour:
Colourless, white
Lustre:
Vitreous
Hardness:
5½
Specific Gravity:
2.93
Crystal System:
Monoclinic
Name:
Named in honor of Jack Eaker (26 October 1930, York County, South Carolina, USA - 28 February 2021, Kings Mountain, Cleveland co, NC, USA), lab analyst for the Foote Mineral Company at Kings Mountain, North Carolina, USA. He discovered the mineral and suspected it was a new species. The name is pronounced ēkerait.
This page provides mineralogical data about Eakerite.
Unique Identifiers
Mindat ID:
1343
Long-form identifier:
mindat:1:1:1343:3
Similar Names
IMA Classification of Eakerite
Approved
IMA Formula:
Ca2Sn4+Al2Si6O18(OH)2·2H2O
Approval year:
1969
First published:
1970
Classification of Eakerite
9.CG.05
9 : SILICATES (Germanates)
C : Cyclosilicates
G : [Si4O12]8- branched 4-membered single rings
9 : SILICATES (Germanates)
C : Cyclosilicates
G : [Si4O12]8- branched 4-membered single rings
72.1.5.1
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
1 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
16.14.12
16 : Silicates Containing Aluminum and other Metals
14 : Aluminosilicates of Ti, Zr, Sn and Pb
16 : Silicates Containing Aluminum and other Metals
14 : Aluminosilicates of Ti, Zr, Sn and Pb
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 |
|---|---|---|
| Ea | 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 Eakerite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Colourless, white
Hardness:
5½ on Mohs scale
Cleavage:
None Observed
Parting:
None observed
Fracture:
Conchoidal
Density:
2.93(1) g/cm3 (Measured) 2.931 g/cm3 (Calculated)
Comment:
Measured flawless crystals by immersion in Clerici solution
Optical Data of Eakerite
Type:
Biaxial (+)
RI values:
nα = 1.584 nβ = 1.586 nγ = 1.600
2V:
Measured: 35° , Calculated: 42°
Max. Birefringence:
δ = 0.016
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:
Moderate (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 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.
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:
small
Chemistry of Eakerite
Mindat Formula:
Ca2SnAl2Si6O18(OH)2 · 2H2O
Element Weights:
Crystallography of Eakerite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/a
Cell Parameters:
a = 15.83 Å, b = 7.72 Å, c = 7.44 Å
β = 101.31°
β = 101.31°
Ratio:
a:b:c = 2.051 : 1 : 0.964
Unit Cell V:
891.57 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Prismatic crystals. Forms, in order of abundance (type material) are: {111}, {210}, {410}, {201}, {20l}, {001}, and {100.}
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0010472 | Eakerite | Uchida H, Downs R T, Thompson R M (2007) Reinvestigation of eakerite, Ca2SnAl2Si6O18(OH)2*2H2O: H-atom positions by single-crystal X-ray diffraction and correlation with Raman spectroscopic data Acta Crystallographica E63 i47-i49 |  | 2007 | Foote Mineral Company mine, Kings Mountain, North Carolina, USA | 0 | 293 |
| 0000529 | Eakerite | Kossiakoff A A, Leavens P B (1976) The crystal structure of eakerite, a calcium-tin silicate American Mineralogist 61 956-962 |  | 1976 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.812 Å | (100) |
| 5.257 Å | (90) |
| 7.31 Å | (80) |
| 3.021 Å | (80) |
| 3.353 Å | (60) |
| 6.905 Å | (50) |
| 5.944 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 22 : Hydration and low-? subsurface aqueous alteration (see also #23) |
Type Occurrence of Eakerite
General Appearance of Type Material:
Transparent prismatic crystals
Place of Conservation of Type Material:
Natural History Museum, London, England, 1968, 204.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 120301, 121143.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 120301, 121143.
Geological Setting of Type Material:
Spodumene-rich pegmatite.
Associated Minerals at Type Locality:
Synonyms of Eakerite
Other Language Names for Eakerite
Common Associates
Associations Based on Photo Data:
Other Information
Notes:
Not soluble in acids or bases.
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 Eakerite
mindat.org URL:
https://www.mindat.org/min-1343.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 Eakerite
Reference List:
Leavens, Peter B., White, John Sampson, Hey, Max H. (1970) Eakerite-- a New Tin Silicate. The Mineralogical Record, 1 (3) Tucson. 92-96
Kossiakoff, Anthony A., Leavens, Peter B. (1976) The crystal structure of eakerite, a calcium-tin silicate. American Mineralogist, 61 (9-10) 956-962
Uchida, Hinako, Downs, Robert T., Thompson, Richard M. (2007) Reinvestigation of eakerite, Ca2SnAl2Si6O18(OH)2·2H2O: H-atom positions by single-crystal X-ray diffraction and correlation with Raman spectroscopic data. Acta Crystallographica Section E Structure Reports Online, 63 (2) 47-49 doi:10.1107/s1600536807002000
Localities for Eakerite
Showing 3 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.
Russia | |
| |
| Ivashchenko et al. (2011, September) | |
USA (TL) | |
| Horton et al. (1981) +2 other references |
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Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA