Jeffreyite
A valid IMA mineral species
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About Jeffreyite
View of the Jeffrey Mine open pit -summer 2011
Jeffrey Mine, Val-des-Sources, Les Sources RCM, Estrie, Québec, Canada
Jeffrey Mine, Val-des-Sources, Les Sources RCM, Estrie, Québec, Canada
Formula:
(Ca,Na)2(Be,Al)(Si2O7,HSi2O7)
Colour:
Colourless
Hardness:
5
Specific Gravity:
2.99
Crystal System:
Orthorhombic
Name:
Named by Joel D. Grice and George W. Robinson in 1984 after the Jeffrey Mine, the type locality.
This page provides mineralogical data about Jeffreyite.
Unique Identifiers
Mindat ID:
2086
Long-form identifier:
mindat:1:1:2086:8
Similar Names
| Geffroyite | A valid IMA mineral species | (Cu,Fe,Ag)9(Se,S)8 |
IMA Classification of Jeffreyite
Approved
IMA Formula:
(Ca,Na)2(Be,Al)Si2(O,OH)7
Approval year:
1982
First published:
1984
Classification of Jeffreyite
9.BB.10
9 : SILICATES (Germanates)
B : Sorosilicates
B : Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination
9 : SILICATES (Germanates)
B : Sorosilicates
B : Si2O7 groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination
55.4.2.3
55 : SOROSILICATES Si2O7 Groups,Generally with no Additional Anions
4 : Si2O7 Groups, Generally with No Additional Anions with cations in [8] and lower coordination
55 : SOROSILICATES Si2O7 Groups,Generally with no Additional Anions
4 : Si2O7 Groups, Generally with No Additional Anions with cations in [8] and lower coordination
14.3.9
14 : Silicates not Containing Aluminum
3 : Silicates of Be
14 : Silicates not Containing Aluminum
3 : Silicates of Be
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 |
|---|---|---|
| Jfy | 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 Jeffreyite
Transparency:
Transparent
Colour:
Colourless
Comment:
Originally found with a brownish cast due to a fungal coating.
Streak:
White
Hardness:
5 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
{001}, {110}
{001}, {110}
Density:
2.99(2) g/cm3 (Measured) 2.98 g/cm3 (Calculated)
Comment:
methylene iodide - methyl alcohol solution at 21C
Optical Data of Jeffreyite
Type:
Biaxial (-)
RI values:
nα = 1.625(2) nβ = 1.641(2) nγ = 1.643(2)
2V:
Measured: 40° (2), Calculated: 39°
Max. Birefringence:
δ = 0.018
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 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:
r < v moderate
Chemistry of Jeffreyite
Mindat Formula:
(Ca,Na)2(Be,Al)(Si2O7,HSi2O7)
Element Weights:
Crystallography of Jeffreyite
Crystal System:
Orthorhombic
Class (H-M):
222 - Disphenoidal
Space Group:
C2221
Cell Parameters:
a = 14.90(1) Å, b = 14.90(1) Å, c = 40.41(8) Å
Ratio:
a:b:c = 1 : 1 : 2.712
Unit Cell V:
8,971.42 ų (Calculated from Unit Cell)
Z:
64
Morphology:
Thin pseudotetragonal plates. The observed forms on the plates include the pinacoid
{001} and a prism, [110].
{001} and a prism, [110].
Twinning:
Twinning was observed on (100).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.774 Å | (100) |
| 2.993 Å | (90) |
| 2.541 Å | (60) |
| 1.755 Å | (50) |
| 5.00 Å | (40) |
| 2.360 Å | (40) |
| 2.229 Å | (40) |
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 Jeffreyite
General Appearance of Type Material:
Micaceous
Place of Conservation of Type Material:
Canadian Museum of Nature, Ottawa, Canada, 48740.
Geological Setting of Type Material:
Rodingitized granite dyke
Associated Minerals at Type Locality:
Synonyms of Jeffreyite
Other Language Names for Jeffreyite
Related Minerals - Strunz-mindat Grouping
| 9.BB.10 | Hardystonite | Ca2Zn[Si2O7] |
| 9.BB.10 | Okayamalite | Ca2B[BSiO7] |
| 9.BB.10 | Alumoåkermanite | (CaNa)Al[Si2O7] |
| 9.BB.10 | Åkermanite | Ca2Mg[Si2O7] |
| 9.BB.10 | 'Ferri-gehlenite' | Ca2Fe3+[AlSiO7] |
| 9.BB.10 | Gehlenite | Ca2Al[AlSiO7] |
| 9.BB.10 | Ferroåkermanite | Ca2Fe[Si2O7] |
| 9.BB.10 | Cebollite | Ca5Al2(SiO4)3(OH)4 |
| 9.BB.10 | Hydroxylgugiaite | (Ca,◻)2(Si,Be)[(Be,Si)2O5.5(OH)1.5] |
| 9.BB.10 | Gugiaite | Ca2Be[Si2O7] |
| 9.BB.15 | Barylite | Be2Ba(Si2O7) |
| 9.BB.15 | 'Barylite-1O' | Be2Ba(Si2O7) |
| 9.BB.20 | Bennesherite | Ba2Fe2+[Si2O7] |
| 9.BB.20 | Andrémeyerite | BaFe2+2(Si2O7) |
Fluorescence of Jeffreyite
None.
Other Information
Notes:
Not readily soluble in 20% HCl.
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 Jeffreyite
mindat.org URL:
https://www.mindat.org/min-2086.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 Jeffreyite
Reference List:
Grice, Joel D., Robinson, George W. (1984) Jeffreyite, (Ca,Na)2(Be,Al)Si2(O,OH)7, a new mineral species and its relation to the melilite group. The Canadian Mineralogist, 22 (3) 443-446
Localities for Jeffreyite
Showing 1 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 (TL) | |
| 179-181. +2 other references |
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Jeffrey Mine, Val-des-Sources, Les Sources RCM, Estrie, Québec, Canada