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Jeffbenite

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Formula:
Mg3Al2Si3O12
Colour:
Deep emerald green
Lustre:
Vitreous
Hardness:
7
Specific Gravity:
3.576 (Calculated)
Crystal System:
Tetragonal
Name:
Jeffbenite is named in honour of two scientists, Jeffrey W. Harris (School of Geographical and Earth Sciences, University of Glasgow, UK; b. 1940) and Ben Harte (School of Geosciences, University of Edinburgh, UK; b. 1941), whose work on diamonds, and super-deep diamonds in particular, has shaped our understanding of mantle geochemical processes for years to come.
Dimorph of:
Isostructural with:
High-pressure polymorph of pyrope.
New structure type.
The petrological importance of jeffbenite is related to its very deep origin, which may allow its use as a pressure marker for detecting super-deep diamonds. Previous experimental work carried out on a Ti-rich jeffbenite establishes that it can be formed at 13 GPa and 1700 K as maximum P-T conditions.
Previously known as TAPP (Tetragonal Almandine-Pyrope Phase).


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Classification of JeffbeniteHide

Approved
Approval Year:
2015
First Published:
2016

Physical Properties of JeffbeniteHide

Vitreous
Transparency:
Transparent
Colour:
Deep emerald green
Hardness:
Hardness:
VHN100= 1346 - Vickers
Tenacity:
Brittle
Cleavage:
None Observed
Fracture:
Irregular/Uneven
Density:
3.576 g/cm3 (Calculated)

Optical Data of JeffbeniteHide

Type:
Uniaxial (-)
RI values:
nω = 1.733(5) nε = 1.721(5)
Max Birefringence:
δ = 0.012
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
High
Pleochroism:
Visible
Comments:
ε = light blue and ω = colourless

Chemical Properties of JeffbeniteHide

Formula:
Mg3Al2Si3O12
Common Impurities:
Fe(II),Cr

Crystallography of JeffbeniteHide

Crystal System:
Tetragonal
Class (H-M):
4 2m - Scalenohedral
Space Group:
I4 2d
Cell Parameters:
a = 6.5231(1) Å, c = 18.1756(3) Å
Ratio:
a:c = 1 : 2.786
Unit Cell V:
773.39 ų (Calculated from Unit Cell)
Z:
4

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
3.069Å(11)
2.881Å(24)
2.647Å(100)
2.220Å(19)
2.056Å(11)
1.625Å(44)
1.390Å(13)
1.372Å(11)
Comments:
From Type Description.

Type Occurrence of JeffbeniteHide

Place of Conservation of Type Material:
Type material is deposited in the collections of the Museum of Mineralogy of the University of Padova, Padova, Italy, catalogue number MMP M12660
Geological Setting of Type Material:
As inclusions inside the so called "super deep diamonds" from São Luiz river alluvials, Brazil
Associated Minerals at Type Locality:

Synonyms of JeffbeniteHide

Fluorescence of JeffbeniteHide

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for JeffbeniteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Nestola, F., Burnham, A., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J. and Gunter, M. (2015) Jeffbenite, IMA 2014-097. CNMNC Newsletter No. 24, April 2015, page 250; Mineralogical Magazine, 79, 247-251.
Nestola, F., Burnham, A.D., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J., Gunter, M., Kohn, S.C. (2016): Tetragonal Almandine-Pyrope Phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineralogical Magazine, 80, 1219-1232.
Anzolini, C., Nestola, F., Burnham, A. D., Peruzzo, L., Tauro, L., Alvaro, M., ... & Kohn, S. C. (2015). Diffraction and spectroscopic characterization of jeffbenite: a high-pressure marker in diamonds. Periodico di Mineralogia, ECMS, 21-22.
J.R. Smyth, F. Wang, E.C. Thompson, S.D. Jacobsen. (2019) Crystal Structure and
Compressibility of Fe – Mg Jeffbenite Synthesized at 15 GPa and 1200°C. Abstract
MR31B-0080, presented at the American Geophysical Union Fall Meeting, San
Francisco, CA, 11 December 2019.

Internet Links for JeffbeniteHide

Localities for JeffbeniteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Brazil (TL)
 
  • Mato Grosso
    • Juína kimberlite field
      • Juína
Nestola, F., Burnham, A., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J. and Gunter, M. (2015) Jeffbenite, IMA 2014-097. CNMNC Newsletter No. 24, April 2015, page 250; Mineralogical Magazine, 79, 247-251; Nestola, F., Burnham, A.D., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J., Gunter, M., Kohn, S.C. (2016): Tetragonal Almandine-Pyrope Phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineralogical Magazine, 80, 1219-1232
Guinea
 
  • Kankan Region
Nestola, F., Burnham, A. D., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M. J., ... & Kohn, S. C. (2016). PREPUBLICATION: Tetragonal Almandine-Pyrope Phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineralogical Magazine.
 
Mineral and/or Locality  
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