Tunellite
A valid IMA mineral species
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About Tunellite
George G. Tunell, Jr.
Formula:
SrB6O9(OH)2 · 3H2O
Colour:
Colourless, grayish white
Lustre:
Sub-Vitreous, Pearly
Hardness:
2½
Specific Gravity:
2.40
Crystal System:
Monoclinic
Name:
Named by R.C. Erd, V. Morgan, and J.R. Clark in 1961 in honor of George Gerard Tunell, Jr. (4 April 1900, Chicago, Illinois, USA - 4 July 1996, Montecito, California, USA), professor of geochemistry, University of California. President of the Mineralogical Society of America (1950) and Roebling Medal recipient in 1973. He made major advances in X-ray crystallography, physical chemistry, and thermodynamic analysis of minerals, especially metallic ores. The name is pronounced tŭn nĕl' īt.
This page provides mineralogical data about Tunellite.
Unique Identifiers
Mindat ID:
4050
Long-form identifier:
mindat:1:1:4050:7
Similar Names
| Tanolite | A synonym of Cordierite |
| Tonalite | A rock classification type |
IMA Classification of Tunellite
Classification of Tunellite
6.FC.05
6 : BORATES
F : Hexaborates
C : Phyllo-hexaborates
6 : BORATES
F : Hexaborates
C : Phyllo-hexaborates
26.6.6.2
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
6 : Hexaborates
9.3.31
9 : Borates
3 : Borates of Ca and Sr
9 : Borates
3 : Borates of Ca and Sr
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 |
|---|---|---|
| Tnl | 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 Tunellite
Sub-Vitreous, Pearly
Transparency:
Transparent
Comment:
Pearly on cleavages
Colour:
Colourless, grayish white
Streak:
White
Hardness:
2½ on Mohs scale
Tenacity:
Flexible
Cleavage:
Perfect
Perfect on {100}
Distinct on {001}
Perfect on {100}
Distinct on {001}
Density:
2.40(1) g/cm3 (Measured) 2.391 g/cm3 (Calculated)
Optical Data of Tunellite
Type:
Biaxial (+)
RI values:
nα = 1.519 nβ = 1.534 nγ = 1.569
2V:
Calculated: 68°
Max. Birefringence:
δ = 0.050
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:
None to Very Low
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 weak
Optical Extinction:
Y = b; X ∧ a = 29°; Z ∧ c = –5°.
Chemistry of Tunellite
Mindat Formula:
SrB6O9(OH)2 · 3H2O
Element Weights:
Elements listed:
Crystallography of Tunellite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Cell Parameters:
a = 14.415(3) Å, b = 8.213(1) Å, c = 9.951(2) Å
β = 114.05°
β = 114.05°
Ratio:
a:b:c = 1.755 : 1 : 1.212
Unit Cell V:
1,075.83 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals to 10 cm elongated on [001]. Flattened tabular with dominant {100}. Compact fine grained nodules. Forms include {100}, {001}, {110}, {011}, and {111}.
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
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Display Options
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Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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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) |
|---|---|---|---|---|---|---|---|
| 0000129 | Tunellite | Clark J R (1964) The crystal structure of tunellite, SrB6O9(OH)2.3H2O American Mineralogist 49 1549-1568 |  | 1964 | Jenifer mine, Kramer borate district, California, USA | 0 | 293 |
| 0018902 | Tunellite | Clark J R (1963) Boron-oxygen polyanion in the crystal structure of tunellite Science 141 1178-1179 | 1963 | Jenifer mine, Kramer borate district, California, USA | 0 | 293 | |
| 0005416 | Tunellite | Burns P C, Hawthorne F C (1994) Hydrogen bonding in tunellite The Canadian Mineralogist 32 895-902 | | 1994 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.57 Å | (100) |
| 4.525 Å | (11) |
| 3.867 Å | (9) |
| 5.138 Å | (8) |
| 3.592 Å | (8) |
| 2.503 Å | (8) |
| 6.78 Å | (7) |
Comments:
Furnace Creek district, California, USA.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
Secondary mineral in borate deposits
Type Occurrence of Tunellite
General Appearance of Type Material:
White compact fine-grained nodules. Also as individual long prismatic crystals up to 1.5 cm in length and equant crystals up to 1 cm in diameter.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, number 123928.
Geological Setting of Type Material:
A secondary mineral in a borate deposit.
Associated Minerals at Type Locality:
Other Language Names for Tunellite
Common Associates
Associations Based on Photo Data:
| 28 photos of Tunellite associated with Ulexite | NaCa[B5O6(OH)6] · 5H2O |
| 8 photos of Tunellite associated with Hydroboracite | CaMg[B3O4(OH)3]2 · 3H2O |
| 3 photos of Tunellite associated with Colemanite | Ca[B3O4(OH)3] · H2O |
| 3 photos of Tunellite associated with Inderite | MgB3O3(OH)5 · 5H2O |
| 1 photo of Tunellite associated with Pararealgar | As4S4 |
Related Minerals - Strunz-mindat Grouping
| 6.FC.05 | Nobleite | CaB6O9(OH)2 · 3H2O |
| 6.FC.10 | Strontioborite | Sr[B8O11(OH)4] |
| 6.FC.15 | Strontioginorite | CaSrB14O20(OH)6 · 5H2O |
| 6.FC.15 | Ginorite | Ca2B14O20(OH)6 · 5H2O |
| 6.FC.20 | Fabianite | CaB3O5(OH) |
Other Information
Notes:
Soluble in cold dilute acid or strong alkaline solutions. Unaffected by glycerol or methanol. In H2SO4, a coating of SrSO4 inhibits further dissolution.
Heated in a closed tube, tunellite exfoliates perpendicular to the cleavage, turns silvery white (resembling muscovite), then turns chalky white. The water driven off has a pH of 4.
Heated in a closed tube, tunellite exfoliates perpendicular to the cleavage, turns silvery white (resembling muscovite), then turns chalky white. The water driven off has a pH of 4.
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 Tunellite
mindat.org URL:
https://www.mindat.org/min-4050.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
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References for Tunellite
Reference List:
Clark, J. R. (1963) Boron-Oxygen Polyanion in the Crystal Structure of Tunellite. Science, 141 (3586). 1178-1179 doi:10.1126/science.141.3586.1178
Clark, Joan R. (1964) The crystal structure of tunellite, SrB6O9(OH)2·3H2O. American Mineralogist, 49 (11-12) 1549-1568
IMA (1967) International Mineralogical Association: Commission on New Minerals and Mineral Names. Mineralogical Magazine and Journal of the Mineralogical Society, 36 (277) 131-136 doi:10.1180/minmag.1967.036.277.20
Localities for Tunellite
Showing 15 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.
Turkey | |
| Helvaci et al. (1991) |
| Helvaci +2 other references | |
| Helvaci et al. (1991) | |
| Helvaci et al. (1991) | |
| Baysal (1972) +1 other reference |
| García-Veigas et al. (2010) +1 other reference |
| American Mineralogist +4 other references |
USA | |
| Erd et al. (1961) +1 other reference |
| Collected it in the mine-Rock Currier +3 other references |
| www.mineralsocal.org (1999) |
| U.S. Borax | |
| Erd et al. (1961) +4 other references |
| Erd et al. (1961) +2 other references | |
| Morgan et al. (1969) +2 other references |
| USGS |
Quick NavTopAbout TunelliteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Rio Tinto Borax Mine, Kramer Borate deposit, Boron, Kern County, California, USA