Hilgardite Mineral Data

Hilgardite Mineral Data +

General Hilgardite Information

Chemical Formula:

Ca2B5O9Cl·(H2O)

Composition:

Molecular Weight = 331.67 gm

Calcium 24.17 % Ca 33.82 % CaO

Boron 16.30 % B 52.48 % B₂O₃

Hydrogen 0.61 % H 5.43 % H₂O

Chlorine 10.69 % Cl 10.69 % Cl

- % Cl -2.41 % -O=Cl₂

Oxygen 48.24 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₂B₅O₉Cl·(H₂O)

Environment:

Minor borate mineral in salt deposits.

IMA Status:

Approved IMA 1979

Locality:

Choctaw Salt Dome, Iberville Parish, Louisiana, USA Link to MinDat.org Location Data.

Name Origin:

Named for Eugene W. Hilgard (1833-1916), German-American geologist, one of the first to describe the Loiuisiana salt dome deposits.

Hilgardite Image

Images:

Hilgardite Boracite

Comments: Sub-mm reddish orange crystals of hilgardite on white boracite.
Location: Boulby Mine, Loftus, Cleveland, Great Britain. Scale: 1.5 x 2.5 cm.
© John Veevaert

Hilgardite Crystallography

Axial Ratios:

a:b:c =0.9741:1:1.0156

Cell Dimensions:

a = 6.297, b = 6.464, c = 6.565, Z = 1; alpha = 74.24°, beta = 61.68°, gamma = 61.26° V = 198.50 Den(Calc)= 2.77

Crystal System:

Triclinic - PedialH-M Symbol (1) Space Group: P1

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

By Intensity(I/I_o): 2.88(1), 2.827(0.83), 2.029(0.64),

Crystal Structure:

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Ghose S , Wan C , American Mineralogist , 64 (1979) p.187-195, Hilgardite, Ca2[B5O9]Cl*H2O: a piezoelectric zeolite-type pentaborate

Physical Properties of Hilgardite

Cleavage:

[010] Perfect, [100] Perfect

Color:

Colorless.

Density:

2.69

Diaphaniety:

Transparent

Hardness:

5 - Apatite

Luster:

Vitreous (Glassy)

Streak:

white

Optical Properties of Hilgardite

Gladstone-Dale:

CI meas= -0.013 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.016 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2323,KPDmeas= 0.2392,KC= 0.2361

Optical Data:

Biaxial (+), a=1.63, b=1.636, g=1.664, bire=0.0340, 2V(Calc)=52, 2V(Meas)=35.

Calculated Properties of Hilgardite

Electron Density:

r_electron=2.66 gm/cc
note: r_Hilgardite=2.69 gm/cc.

Fermion Index

Fermion Index = 0.03298
Boson Index = 0.96702

Photoelectric:

PE_Hilgardite= 3.87 barns/electron
U=PE_Hilgardite x r_electron= 10.30 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Hilgardite is Not Radioactive

Hilgardite Classification

Dana Class:

26.5.14.1 (26)Hydrated Borates Containing Hydroxyl or Halogen

(26.5)Dana Type

(26.5.14)Dana Group

26.5.14.1 Hilgardite Ca2B5O9Cl·(H2O) P1 1

26.5.14.2 Kurgantaite! CaSr[B5O9]Cl·(H2O) P1 1

Strunz Class:

V/K.04-10 V - Nitrates, Carbonates and Borates

V/K - Layered borates with complex groups [Bx(O,OH)y]

V/K.04 - Hilgardite-1Tc - Heidornite series

V/K.04-10 Hilgardite Ca2B5O9Cl·(H2O) P1 1

V/K.04-30 Tyretskite Ca2B5O9(OH)·(H2O) P1 1

V/K.04-40 Heidornite Na2Ca3B5O8(SO4)2Cl(OH)2 C 2/c 2/m

Other Hilgardite Information

References:

NAME( Dana8) PHYS. PROP.(Am.Min.,Vol.78,p1313,1993) OPTIC PROP.(Am.Min.,Vol.78,p1313,1993)

See Also:

Links to other databases for Hilgardite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 -Google Images 4 -Google Scholar 5 -Handbook of Mineralogy (UofA) 6 -MinDAT 7 -MinMax(Deutsch) 8 -MinMax(English) 9 -Mineralienatlas (Deutsch) 10 -QUT Mineral Atlas 11 - WWW-MINCRYST

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Print or Cut-and-Paste your Hilgardite Specimen Label here :

Hilgardite

Ca2B5O9Cl·(H2O)
Dana No: 26.5.14.1 Strunz No: V/K.04-10
Locality:

Notes: