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.

Type Locality:

ⓘ São Luis river alluvials, Juína, Mato Grosso, Brazil

Dimorph of:

Pyrope

Isostructural with:

Arsenudinaite, Niasite, Udinaite

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).

Unique IdentifiersHide

Mindat ID:

46574

Long-form identifier:

mindat:1:1:46574:4

IMA Classification of JeffbeniteHide

IMA status:

Approved

Approval year:

2015

First published:

2016

Classification of JeffbeniteHide

Strunz-mindat (2026):

9.AD.55

9 : SILICATES (Germanates)
A : Nesosilicates
D : Nesosilicates without additional anions; cations in [6] and/or greater coordination

Mineral SymbolsHide

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
Jef	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 JeffbeniteHide

Lustre:

Vitreous

Transparency:

Transparent

Colour:

Deep emerald green

Hardness:

7 on Mohs scale

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:

n_ω = 1.733(5) n_ε = 1.721(5)

Max. Birefringence:

δ = 0.012
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.

Thickness: 30 µm Order divisions

Rotation:

Surface Relief:

Very High (positive)
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.

Focus:

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.

Thickness: 30 µm

Pleochroism:

Visible

Comments:

ε = light blue and ω = colourless

Chemistry of JeffbeniteHide

Mindat Formula:

Mg₃Al₂Si₃O₁₂

Element Weights:

Element	% weight
O	47.626 %
Si	20.901 %
Mg	18.087 %
Al	13.386 %

Calculated from ideal end-member formula.

Elements listed:

Al, Mg, O, Si - search for minerals with similar chemistry

Common Impurities:

Fe(II),Cr

Crystallography of JeffbeniteHide

Crystal System:

Tetragonal

Class (H-M):

42m - Scalenohedral

Space Group:

I42d

Cell Parameters:

a = 6.5231(1) Å, c = 18.1756(3) Å

Ratio:

a:c = 1 : 2.786

Unit Cell V:

773.39 Å³ (Calculated from Unit Cell)

Crystal StructureHide

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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)
0002596	Jeffbenite	Finger L W, Conrad P G (2000) The crystal structure of "Tetragonal Almandine-Pyrope Phase" (TAPP): A reexamination American Mineralogist 85 1804-1807		2000		0	293

CIF Raw Data - click here to close

data_global
_chemical_name_mineral 'Jeffbenite'
loop_
_publ_author_name
'Finger L W'
'Conrad P G'
_journal_name_full 'American Mineralogist'
_journal_volume 85 
_journal_year 2000
_journal_page_first 1804
_journal_page_last 1807
_publ_section_title
;
 The crystal structure of "Tetragonal Almandine-Pyrope Phase" (TAPP):
 A reexamination
;
_database_code_amcsd 0002596
_chemical_formula_sum 'Si2.91 Al1.942 Fe.49 Mg2.658 O12'
_cell_length_a 6.5269
_cell_length_b 6.5269
_cell_length_c 18.1835
_cell_angle_alpha 90
_cell_angle_beta 90
_cell_angle_gamma 90
_cell_volume 774.625
_exptl_crystal_density_diffrn      3.585
_symmetry_space_group_name_H-M 'I -4 2 d'
loop_
_space_group_symop_operation_xyz
  'x,y,z'
  '1/2+x,1/2+y,1/2+z'
  '1/2-y,-x,3/4+z'
  '-y,1/2-x,1/4+z'
  'y,-x,-z'
  '1/2+y,1/2-x,1/2-z'
  '-x,1/2+y,1/4-z'
  '1/2-x,+y,3/4-z'
  '-x,-y,z'
  '1/2-x,1/2-y,1/2+z'
  '1/2+y,x,3/4+z'
  '+y,1/2+x,1/4+z'
  '-y,x,-z'
  '1/2-y,1/2+x,1/2-z'
  'x,1/2-y,1/4-z'
  '1/2+x,-y,3/4-z'
loop_
_atom_site_label
_atom_site_fract_x
_atom_site_fract_y
_atom_site_fract_z
_atom_site_occupancy
Si1   0.50000   0.50000   0.00000   1.00000
Si2  -0.14990   0.25000   0.12500   0.95500
Al2  -0.14990   0.25000   0.12500   0.04500
Fe1   0.00000   0.00000   0.00000   0.21000
Mg1   0.00000   0.00000   0.00000   0.79000
Fe2   0.25990   0.25000   0.12500   0.07400
Al2   0.25990   0.25000   0.12500   0.92600
Fe3   0.00000   0.50000  -0.02296   0.06600
Mg3   0.00000   0.50000  -0.02296   0.93400
O1   0.01870   0.28090   0.05760   1.00000
O2  -0.26140   0.03720   0.10130   1.00000
O3   0.43680   0.29610   0.04680   1.00000
loop_
_atom_site_aniso_label
_atom_site_aniso_U_11
_atom_site_aniso_U_22
_atom_site_aniso_U_33
_atom_site_aniso_U_12
_atom_site_aniso_U_13
_atom_site_aniso_U_23
Si1 0.00468 0.00468 0.00620 0.00000 0.00000 0.00000
Si2 0.00632 0.00533 0.00519 0.00000 0.00000 0.00000
Al2 0.00632 0.00533 0.00519 0.00000 0.00000 0.00000
Fe1 0.00887 0.00887 0.01223 0.00000 0.00000 0.00000
Mg1 0.00887 0.00887 0.01223 0.00000 0.00000 0.00000
Fe2 0.00747 0.00658 0.00536 0.00000 0.00000 0.00000
Al2 0.00747 0.00658 0.00536 0.00000 0.00000 0.00000
Fe3 0.00747 0.00645 0.00704 0.00052 0.00000 0.00000
Mg3 0.00747 0.00645 0.00704 0.00052 0.00000 0.00000
O1 0.00596 0.00835 0.00804 -0.00140 0.00180 0.00180
O2 0.01077 0.00723 0.00972 -0.00088 -0.00066 -0.00066
O3 0.01051 0.00609 0.00821 0.00000 0.00066 0.00066

X-Ray Powder DiffractionHide

Powder Diffraction Data:

d-spacing	Intensity
3.069 Å	(11)
2.881 Å	(24)
2.647 Å	(100)
2.220 Å	(19)
2.056 Å	(11)
1.625 Å	(44)
1.390 Å	(13)
1.372 Å	(11)

Locality:

São Luis river alluvials, Juína, Mato Grosso, Brazil

Comments:

From Type Description.

Geological EnvironmentHide

Paragenetic Mode(s):

Paragenetic Mode	Earliest Age (Ga)
Stage 4b: Highly evolved igneous rocks	>3.0
36 : Carbonatites, kimberlites, and related igneous rocks

Type Occurrence of JeffbeniteHide

Type Locality:

ⓘ São Luis river alluvials, Juína, Mato Grosso, Brazil

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:

Enstatite

'Fayalite-Forsterite Series'

'Ferropericlase'

Walstromite

Synonyms of JeffbeniteHide

IMA2014-097

TAPP

Tetragonal Almandine-Pyrope Phase

UM1997-49-SiO:AlFeMg

Other Language Names for JeffbeniteHide

Dutch:Jeffbeniet

German:Jeffbenit

Related Minerals - Strunz-mindat Grouping Hide

9.AD.	Adrianite	Ca₁₂(Al₄Mg₃Si₇)O₃₂Cl₆	Iso. 43m : I43d
9.AD.05	Larnite	Ca₂SiO₄	Mon. 2/m
9.AD.10	Calcio-olivine	Ca₂SiO₄	Orth. mmm(2/m2/m2/m)
9.AD.15	Merwinite	Ca₃Mg(SiO₄)₂	Mon. 2/m : P2₁/b
9.AD.20	Bredigite	Ca₇Mg(SiO₄)₄	Orth. mm2 : Pnn2
9.AD.25	Midbarite	Ca₃Mg₂(V⁵⁺₂Si)O₁₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Menzerite-(Y)	(Y₂Ca)Mg₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Uvarovite	Ca₃Cr³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Eltyubyuite	Ca₁₂Fe³⁺₁₀Si₄O₃₂Cl₆	Iso. 43m : I43d
9.AD.25	Eringaite	Ca₃Sc₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Henritermierite	Ca₃Mn³⁺₂(SiO₄)₂[◻(OH)₄]	Tet. 4/mmm(4/m2/m2/m) : I4₁/acd
9.AD.25 va	'Hydrougrandite'	(Ca,Mg,Fe²⁺)₃(Fe³⁺,Al)₂[(OH)₄(SiO₄)₂]	Iso.
9.AD.25	Calderite	Mn²⁺₃Fe³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Nikmelnikovite	Ca₁₂(Fe²⁺Fe³⁺₃Al₃◻)[SiO₄]₆[◻(OH)₄]₅◻₄	Trig. 3 : R3
9.AD.25	Hutcheonite	Ca₃Ti₂(SiO₄)(AlO₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Wadalite	(Ca,Mg)₆(Al,Fe³⁺)₄((Si,Al)O₄)₃O₄Cl₃	Iso. 43m : I43d
9.AD.25	Rubinite	Ca₃Ti³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Kerimasite	Ca₃Zr₂(SiO₄)(Fe³⁺O₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Holtstamite	Ca₃Al₂(SiO₄)₂[◻(OH)₄]	Tet. 4/mmm(4/m2/m2/m) : I4₁/acd
9.AD.25	Spessartine	Mn²⁺₃Al₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Toturite	Ca₃Sn₂(SiO₄)(Fe³⁺O₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Kimzeyite	Ca₃Zr₂(SiO₄)(AlO₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	'Khoharite'	Mg₃Fe³⁺₂(SiO₄)₃
9.AD.25	Irinarassite	Ca₃Sn₂(SiO₄)(AlO₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Knorringite	Mg₃Cr³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Goldmanite	Ca₃V³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	'Blythite'	Mn²⁺₃Mn³⁺₂[SiO₄]₃
9.AD.25	'Skiagite'	Fe²⁺₃Fe³⁺₂[SiO₄]₃
9.AD.25	'UM1984-37-SiO:CrMn'	Mn²⁺₃Cr³⁺₂(SiO₄)₃
9.AD.25	Almandine	Fe²⁺₃Al₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25 va	'Yamatoite'	(Mn²⁺,Ca)₃(V³⁺,Al)₂(SiO₄)₃	Iso.
9.AD.25	Momoiite	Mn²⁺₃V³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Grossular	Ca₃Al₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Andradite	Ca₃Fe³⁺₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Morimotoite	Ca₃(TiFe²⁺)(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Majorite	Mg₃(MgSi)(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Pyrope	Mg₃Al₂(SiO₄)₃	Iso. m3m(4/m32/m) : Ia3d
9.AD.25	Schorlomite	Ca₃Ti₂(SiO₄)(Fe³⁺O₄)₂	Iso. m3m(4/m32/m) : Ia3d
9.AD.30	Hafnon	Hf(SiO₄)	Tet. 4/mmm(4/m2/m2/m) : I4₁/amd
9.AD.30	Zircon	Zr(SiO₄)	Tet. 4/mmm(4/m2/m2/m) : I4₁/amd
9.AD.30	Coffinite	U(SiO₄) · nH₂O	Tet. 4/mmm(4/m2/m2/m) : I4₁/amd
9.AD.30	Thorite	Th(SiO₄)	Tet. 4/mmm(4/m2/m2/m) : I4₁/amd
9.AD.30 va	'Auerlite'	near Th(Si,P)O₄
9.AD.30	Stetindite-(Ce)	Ce⁴⁺SiO₄	Tet. 4/mmm(4/m2/m2/m) : I4₁/amd
9.AD.35	'Tombarthite-(Y)'	Y₄(Si,H₄)₄O_12-x(OH)_4+2x	Mon.
9.AD.35	Huttonite	ThSiO₄	Mon. 2/m
9.AD.40	Eulytine	Bi₄(SiO₄)₃	Iso. 43m : I43d
9.AD.45	Reidite	Zr(SiO₄)	Tet. 4/m : I4₁/a

Fluorescence of JeffbeniteHide

In UV light:

none

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.

Internet Links for JeffbeniteHide

mindat.org URL:

https://www.mindat.org/min-46574.html
Please feel free to link to this page.

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External Links:

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Raman and XRD data at RRUFF project

References and PDF downloads at RRUFF project

American Mineralogist Crystal Structure Database

Handbook of Mineralogy page PDF

Mineral Dealers:

Buy from D. Joyce minerals

References for JeffbeniteHide

Reference List:

Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2015) New minerals and nomenclature modifications approved in 2015, CNMNC Newsletter No 24. Mineralogical Magazine, 79 (2) 247-251 doi:10.1180/minmag.2015.079.2.03

Anzolini, C., Nestola, F., Burnham, A. D., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J., Gunther, M., Kohn, S. C. (2015) Diffraction and spectroscopic characterization of jeffbenite: a high-pressure marker in diamonds. Periodico di Mineralogia, ECMS, 21-22.

Nestola, F., Burnham, A.D., Peruzzo, L., Tauro, L., Alvaro, M., Walter, M.J., Gunter, M., Anzolini, C., Kohn, S.C. (2016) Tetragonal Almandine-Pyrope Phase, TAPP: finally a name for it, the new mineral jeffbenite. Mineralogical Magazine, 80, 1219-1232.

(2017) Jeffbenite. Handbook of Mineralogy. Mineralogical Society of America

Smyth, J.R., Wang, F., Thompson, E.C., Jacobsen, S.D. (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.

Localities for JeffbeniteHide

Showing 8 localities.

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.

Hide all sections | Show all sections

Locality ListHide

- 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). ~~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 (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.


Brazil
Mato Grosso Juína ⓘ Collier 4 kimberlite pipe	Bulanova et al. (2010)
ⓘ Juína 5 kimberlite pipe	Thomson et al. (2014)
ⓘ São Luis river alluvials (TL)	Hålenius et al. (2015) +2 other references
ⓘ Sorriso river	Hayman et al. (2005)

Guinea
Kankan Region Kankan Prefecture ⓘ Kankan diamond District	Nestola et al. (2016)

Romania
Sălaj County Ileanda Răstoci ⓘ Măgurici Cave ?	Onac et al. (2003)

Russia
Sakhalin Oblast Kuril Islands Severo-Kurilsky District Atlasov Island Alaid volcano ⓘ Taketomi flank eruption	Zhitova et al. (2025)

South Africa
Northern Cape Namakwa District Municipality Kamiesberg Local Municipality ⓘ Zandkopsdrift carbonatite complex	Ogungbuyi et al. (2022)

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Jeffbenite

About JeffbeniteHide