Log In
Libbyite
A valid IMA mineral species
This page is currently not sponsored. Click here to sponsor this page.
About Libbyite
Willard Frank Libby (December 17, 1908 – September 8, 1980)
Formula:
(NH4)2(Na2◻)[(UO2)2(SO4)3(H2O)]2 · 7H2O
Colour:
light green
Lustre:
Vitreous
Hardness:
2½
Specific Gravity:
3.465 (Calculated)
Crystal System:
Tetragonal
Name:
Libbyite is named in honour of American nuclear chemist Willard F. Libby (December 17, 1908 – September 8, 1980) for his work on nuclear and radiochemistry. Dr. Libby developed the method of radiocarbon dating (published in 1952) for which he was awarded the Nobel Prize in Chemistry for 1960.
This page provides mineralogical data about Libbyite.
Unique Identifiers
Mindat ID:
470492
Long-form identifier:
mindat:1:1:470492:4
Similar Names
| Leboite | A synonym of 'Ferdisilicite' |
IMA Classification of Libbyite
Classification of Libbyite
7.EC.
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
C : With medium-sized and large cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
C : With medium-sized and large cations
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 |
|---|---|---|
| Ly | 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 Libbyite
Vitreous
Transparency:
Transparent
Colour:
Light green
Streak:
Very pale green yellow
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Very Good
excellent on {001}
excellent on {001}
Fracture:
Sub-Conchoidal
Density:
3.465 g/cm3 (Calculated)
Optical Data of Libbyite
Type:
Uniaxial (-)
RI values:
nω = 1.581(2) nε = 1.540(2)
Max. Birefringence:
δ = 0.041
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 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.
Pleochroism:
Visible
Comments:
The pleochroism is O yellow, E pale yellow; O > E.
Blue Lizard Mine, Red Canyon Mining District, San Juan County, Utah, USA