Holtite Mineral Data

Holtite Mineral Data +

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General Holtite Information

Chemical Formula:

Al6(Al,Ta)(BO3)[(SiO4,SbO4,AsO4)]3(O,OH)3

Composition:

Molecular Weight = 2,589.58 gm

Tantalum 10.48 % Ta 12.80 % Ta₂O₅

Aluminum 24.17 % Al 45.67 % Al₂O₃

Iron 0.22 % Fe 0.28 % FeO

Silicon 11.50 % Si 24.59 % SiO₂

Boron 1.59 % B 5.11 % B₂O₃

Antimony 5.64 % Sb 7.50 % Sb₂O₅

Arsenic 2.03 % As 3.11 % As₂O₅

Hydrogen 0.08 % H 0.73 % H₂O

Oxygen 44.30 % O

______ ______

100.00 % 99.78 % = TOTAL OXIDE

Empirical Formula:

Al_23.2Ta_1.5Fe²⁺_0.1B_3.8Si_10.6Sb_1.2As_0.7O_69.6(OH)_2.1

Environment:

As coatings on stibiotantalite and replacing tantalite in a pegmatite.

IMA Status:

Approved IMA 1971

Locality:

At Bunbury Gully, Greenbushes, Western Australia. Link to MinDat.org Location Data.

Name Origin:

Named for Harold Edward Holt (1908-1967), Prime minister of Australia (1966-1967).

Synonym:

ICSD 66143

PDF 25-1209

Holtite Image

Images:

Holtite

Comments: Pale violet crystalline granular holtite in pegmatite.
Location: Vasin-Myl'k Mountain, Voron'i Tundry, Kola Peninsula, Murmansk District, Russia. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Holtite Crystallography

Axial Ratios:

a:b:c =0.3943:1:1.7134

Cell Dimensions:

a = 4.6914, b = 11.896, c = 20.383, Z = 1; V = 1,137.55 Den(Calc)= 3.78

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: P nma

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 10.28(1), 2.94(0.4), 5.89(0.34),

Crystal Structure:

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drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
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S - Stereo Pair on/off
H - Help Screen
I - Data Info
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Hoskins B F , Mumme W G , Pryce M W , Mineralogical Magazine , 53 (1989) p.457-463, Holtite, (Si2.25Sb0.75)B[Al6(Al0.43 Ta0.27[]0.30)O15(O,OH)2.25]:, crystal structure and crystal chemistry, Locality: Greenbrushes, Australia

Physical Properties of Holtite

Cleavage:

[001] Distinct

Color:

Beige white, Brown, Greenish, Greenish brown, Light brown white.

Density:

3.6 - 3.9, Average = 3.75

Diaphaniety:

Semitransparent

Habit:

Blocky - Crystal shape tends to be equant (e.g. feldspars).

Habit:

Pseudo Hexagonal - Crystals show a hexagonal outline.

Hardness:

8.5 - Chrysoberyl

Luminescence:

Fluorescent, Short UV=bright yellow, Long UV=dull orange.

Luster:

Vitreous - Resinous

Streak:

white

Optical Properties of Holtite

Gladstone-Dale:

CI meas= -0.007 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.001 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1953,KPDmeas= 0.1968,KC= 0.1955

Optical Data:

Biaxial (-), a=1.705-1.746, b=1.728-1.759, g=1.73-1.761, bire=0.0150-0.0250, 2V(Calc)=32-42, 2V(Meas)=20-55. Dispersion r < v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

yellow.

Calculated Properties of Holtite

Electron Density:

r_electron=3.62 gm/cc
note: r_Holtite=3.78 gm/cc.

Fermion Index

Fermion Index = 0.00879
Boson Index = 0.99121

Photoelectric:

PE_Holtite= 132.55 barns/electron
U=PE_Holtite x r_electron= 480.27 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Holtite is Not Radioactive

Holtite Classification

Dana Class:

54.1.3.1 (54)Nesosilicate Borosilicates and Some Beryllosilicates

(54.1)with (BO3)

(54.1.3)Dana Group

54.1.3.1 Holtite Al6(Al,Ta)(BO3)[(SiO4,SbO4,AsO4)]3(O,OH)3 P nma 2/m 2/m 2/m

Strunz Class:

VIII/B.31-30 VIII - Silicates

VIII/B - Nesosubsilicates, with anions unfamiliar to tetraheders, with beryllium and boron

VIII/B.31 - Kornerupine - Harkerite series

VIII/B.31-10 Kornerupine (Mg,Fe)4(Al,Fe)6(SiO4,BO4)5(O,OH)2 C mcm 2/m 2/m 2/m

VIII/B.31-12 Prismatine! ([],Fe,Mg)(Mg,Al,Fe)5Al4Si2(Si,Al)2(B,Si,Al)(O,OH,F)22 C mcm 2/m 2/m 2/m

VIII/B.31-15 Magnesiodumortierite (Mg,Ti,[])<1(Al,Mg)2Al4Si3O18-y(OH)yBy=2-3 Pmcn 2/m 2/m 2/m

VIII/B.31-20 Dumortierite Al6.5-7(BO3)(SiO4)3(O,OH)3 Pcmn 2/m 2/m 2/m

VIII/B.31-30 Holtite Al6(Al,Ta)(BO3)[(SiO4,SbO4,AsO4)]3(O,OH)3 P nma 2/m 2/m 2/m

VIII/B.31-40 Grandidierite (Mg,Fe)Al3(BO4)(SiO4)O Pbnm 2/m 2/m 2/m

VIII/B.31-42 Ominelite! (Fe,Mg)Al3BSiO9 Pbnm 2/m 2/m 2/m

VIII/B.31-45 Boralsilite! Al16B6Si2O27 C 2/m 2/m

VIII/B.31-50 Werdingite (Mg,Fe)2Al14B4Si4O37 P1 1

VIII/B.31-60 Harkerite Ca24Mg8Al2(SiO4)8(BO3)6(CO3)10·2(H2O) R 3m 3 2/m

Other Holtite Information

References:

NAME( AntBidBlaNic2) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic2)

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Holtite

Al6(Al,Ta)(BO3)[(SiO4,SbO4,AsO4)]3(O,OH)3
Dana No: 54.1.3.1 Strunz No: VIII/B.31-30
Locality:

Notes: