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Brannockite

A valid IMA mineral species
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06717890017552056059241.jpg
Brannockite

Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
04969950017271921653070.jpg
Brannockite, etc.

Washington Pass, Golden Horn Batholith, Okanogan County, Washington, USA
04979790017552057938336.jpg
Brannockite, etc.

Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
07584770017366703696250.jpg
Brannockite

Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
04969950017271921653070.jpg
Brannockite, etc.

Washington Pass, Golden Horn Batholith, Okanogan County, Washington, USA
03091110017362966227554.jpg
Brannockite, etc.

Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
06717890017552056059241.jpg
Brannockite

Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
04969950017271921653070.jpg
Brannockite, etc.

Washington Pass, Golden Horn Batholith, Okanogan County, Washington, USA
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About BrannockiteHide

09735910017271921742009.jpg
Kent C. Brannock
Formula:
K◻2Sn2Li3[Si12O30]
Colour:
Colorless
Lustre:
Vitreous
Hardness:
5 - 6
Specific Gravity:
2.98
Crystal System:
Hexagonal
Member of:
Osumilite Group
Name:
Named by John S. White Jr., J.E. Arem, J.A. Nelen, P.B. Leavens, and R.W. Thomssen in 1973 in honor of Dr. Kent Combs Brannock (20 July 1923, Independence, Virginia, USA - 21 February 1973, Kingsport, Tennesse, USA), chemist and mineral collector. He did a lot of early collecting at the type locality (Foote Mine).
One of two K-Li-Sn minerals (2024); the other is aleksandrovite.


Unique IdentifiersHide

Mindat ID:
755
Long-form identifier:
mindat:1:1:755:9

Similar NamesHide

IMA Classification of BrannockiteHide

IMA status:
Approved
IMA Formula:
KSn4+2(Li3Si12)O30
Approval year:
1972
First published:
1973

Classification of BrannockiteHide

Strunz-mindat (2026):
9.CM.05

9 : SILICATES (Germanates)
C : Cyclosilicates
M : [Si6O18]12- 6-membered double rings (sechser-Doppelringe)
Dana 8th ed.:
63.2.1a.1

63 : CYCLOSILICATES Condensed Rings
2 : Condensed Rings (Milarite - Osumilite group)
Hey's CIM Ref.:
14.12.1

14 : Silicates not Containing Aluminum
12 : Silicates of Sn

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.

SymbolSourceReference for Standard
BraIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43
BraThe Canadian Mineralogist (2019)The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download

Physical Properties of BrannockiteHide

Lustre:
Vitreous
Transparency:
Transparent
Colour:
Colorless
Comment:
semitransparent
Streak:
White
Hardness:
5 - 6 on Mohs scale
Tenacity:
Brittle
Cleavage:
None Observed
Density:
2.98 g/cm3 (Measured)    3.08 g/cm3 (Calculated)

Optical Data of BrannockiteHide

Type:
Uniaxial (-)
RI values:
nω = 1.567 nε = 1.566
Max. Birefringence:
δ = 0.001
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.

Surface Relief:
Low (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.
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.

Chemistry of BrannockiteHide

Mindat Formula:
K◻2Sn2Li3[Si12O30]
Element Weights:
Element% weight
O43.073 %
Si30.244 %
Sn21.306 %
K3.509 %
Li1.869 %

Calculated from ideal end-member formula.
O
Si
Sn
K
Li
Elements listed:
K, Li, O, Si, Sn - search for minerals with similar chemistry
Common Impurities:
Na

Crystallography of BrannockiteHide

Crystal System:
Hexagonal
Class (H-M):
6/mmm(6/m2/m2/m) - Dihexagonal Dipyramidal
Space Group:
P6/mcc
Cell Parameters:
a = 10.01 Å, c = 14.24 Å
Ratio:
a:c = 1 : 1.423
Unit Cell V:
1,235.69 ų (Calculated from Unit Cell)
Morphology:
Plates, showing {001} (dominant), {100}, {110}, and {114). The ratio of thickness to width is about 1:20.
Twinning:
common, perpendicular to [0001] (observable by X-Ray analysis only)

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0001159BrannockiteArmbruster T, Oberhansli R (1988) Crystal chemistry of double-ring silicates: Structures of sugilite and brannockite American Mineralogist 73 595-60019880293
0001158BrannockiteArmbruster T, Oberhansli R (1988) Crystal chemistry of double-ring silicates: Structures of sugilite and brannockite American Mineralogist 73 595-60019880293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
4.109 Å(100)
2.905 Å(90)
7.141 Å(80)
4.343 Å(80)
5.714 Å(70)
8.693 Å(60)
2.681 Å(60)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 4b: Highly evolved igneous rocks>3.0
34 : Complex granite pegmatites
35 : Ultra-alkali and agpaitic igneous rocks

Type Occurrence of BrannockiteHide

Type Locality:
ⓘ Foote Lithium Co. Mine, Kings Mountain, Cleveland County, North Carolina, USA
General Appearance of Type Material:
Very thin hexagonal plates, to 1 mm; {0001} form dominates.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 125045.
Geological Setting of Type Material:
Vugs and fractures of late-hydrothermal parts of a Li-Sn pegmatite.
Associated Minerals at Type Locality:
AlbiteBavenitePyriteQuartzTitanite

Synonyms of BrannockiteHide

Other Language Names for BrannockiteHide

Relationship of Brannockite to other SpeciesHide

Member of:
Osumilite Group
Other Members of Osumilite Group:
Agakhanovite-(Y)K◻2(YCa)Be3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
AlmaruditeK◻2Mn2+2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mmm
AluminosugiliteKNa2Al2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
ArmeniteBa(H2O)2Ca2Al3[Al3Si9O30]Orth. mmm(2/m2/m2/m) : Pnna
BerezanskiteK◻2Ti2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
ChayesiteK◻2Mg2(Mg2Fe3+)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
DarapiositeKNa2Mn2(Zn2Li)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
DusmatoviteK(K◻)Mn2+2Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
EifeliteKNa2(MgNa)Mg3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
FriedrichbeckeiteK(◻Na)Mg2(Be2Mg)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
KlöchiteK◻2(Fe2+Fe3+)Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P63/mmc
LaurentthomasiteK◻2Mg2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
MerrihueiteK(◻Na)Fe2+2Fe2+3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
MilariteK(◻H2O)Ca2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
OftedaliteK◻2(ScCa)Be3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
OsumiliteK◻2Fe2+2Al3[Al2Si10O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
Osumilite-(Mg)K◻2Mg2Al3[Al2Si10O30] Hex. 6/mmm(6/m2/m2/m) : P6/mcc
PlechoviteCa2[K(H2O)]KBe3Si12O30Hex. 6/mmm(6/m2/m2/m) : P6/mcc
PoudretteiteK◻2Na2B3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
RoedderiteK(◻Na)Mg2Mg3[Si12O30]Hex. 6m2 : P62c
ShibkoviteK(◻K)Ca2Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
SogdianiteK◻2Zr2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
SugiliteKNa2Fe3+2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
Trattnerite◻(◻)2Fe3+2Mg3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
'UM1990-73-SiO:KMnNaZn'K(KNa0.5◻0.5)(Mn1.5Na0.5)Zn3[Si12O30]Hex.
'Unnamed (Mn3+-dominant analog of Sugilite)'KNa2Mn3+2Li3[Si12O30]
YagiiteNa◻2Mg2Al3[Al2Si10O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc

Common AssociatesHide

Associations Based on Photo Data:
6 photos of Brannockite associated with ChamositeFe2+5Al(AlSi3O10)(OH)8
6 photos of Brannockite associated with MicroclineK(AlSi3O8)
1 photo of Brannockite associated with VivianiteFe2+Fe2+2(PO4)2 · 8H2O
1 photo of Brannockite associated with AlbiteNa(AlSi3O8)

Related Minerals - Strunz-mindat GroupingHide

9.CM.Agakhanovite-(Y)K◻2(YCa)Be3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.PlechoviteCa2[K(H2O)]KBe3Si12O30Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05FriedrichbeckeiteK(◻Na)Mg2(Be2Mg)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05LaurentthomasiteK◻2Mg2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05'UM1990-73-SiO:KMnNaZn'K(KNa0.5◻0.5)(Mn1.5Na0.5)Zn3[Si12O30]Hex.
9.CM.05EifeliteKNa2(MgNa)Mg3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05AlmaruditeK◻2Mn2+2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mmm
9.CM.05ArmeniteBa(H2O)2Ca2Al3[Al3Si9O30]Orth. mmm(2/m2/m2/m) : Pnna
9.CM.05MerrihueiteK(◻Na)Fe2+2Fe2+3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05OftedaliteK◻2(ScCa)Be3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05RoedderiteK(◻Na)Mg2Mg3[Si12O30]Hex. 6m2 : P62c
9.CM.05ShibkoviteK(◻K)Ca2Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05SogdianiteK◻2Zr2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05MilariteK(◻H2O)Ca2(Be2Al)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05BerezanskiteK◻2Ti2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05PoudretteiteK◻2Na2B3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05DarapiositeKNa2Mn2(Zn2Li)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05ChayesiteK◻2Mg2(Mg2Fe3+)[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05Osumilite-(Mg)K◻2Mg2Al3[Al2Si10O30] Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05OsumiliteK◻2Fe2+2Al3[Al2Si10O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05SugiliteKNa2Fe3+2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05Trattnerite◻(◻)2Fe3+2Mg3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05KlöchiteK◻2(Fe2+Fe3+)Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P63/mmc
9.CM.05DusmatoviteK(K◻)Mn2+2Zn3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.05YagiiteNa◻2Mg2Al3[Al2Si10O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.9.CM.AluminosugiliteKNa2Al2Li3[Si12O30]Hex. 6/mmm(6/m2/m2/m) : P6/mcc
9.CM.10FaizieviteK2Na(Ca6Na)Ti4Li6[Si6O18]2[Si12O30]F2Tric. 1 : P1

RadioactivityHide

Radioactivity:
Element % Content Activity (Bq/kg) Radiation Type
Uranium (U) 0.0000% 0 α, β, γ
Thorium (Th) 0.0000% 0 α, β, γ
Potassium (K) 3.5086% 1,088 β, γ

For comparison:

  • Banana: ~15 Bq per fruit
  • Granite: 1,000–3,000 Bq/kg
  • EU exemption limit: 10,000 Bq/kg

Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.

Interactive Simulator:

Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!

Activity: –

DistanceDose rateRisk
1 cm
10 cm
1 m

The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).

D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield

Fluorescence of BrannockiteHide

In UV light:
bright bluish white (SW)

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 BrannockiteHide

References for BrannockiteHide

Localities for BrannockiteHide

Showing 4 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.
Tajikistan
 
  • Districts of Republican Subordination
Agakhanov et al. (2016)
USA (TL)
 
  • North Carolina
    • Cleveland County
      • Kings Mountain
White et al. (1973) +2 other references
    • Gaston County
  • Washington
    • Okanogan County
      • Golden Horn Batholith
Raschke (2015) +1 other reference
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