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.

Name Pronunciation:

Hilgardite + Pronunciation

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 - Pedial H-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),

Physical Properties of Hilgardite

Cleavage:

{010} Perfect, {100} Perfect

Color:

Colorless.

Density:

2.69

Diaphaneity:

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= -0.021 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2409,KPDmeas= 0.2392,KC= 0.2361
Ncalc = 1.63 - 1.64

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:

Bulk Density (Electron Density)=2.66 gm/cc
note: Specific Gravity of Hilgardite =2.69 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Hilgardite= 3.87 barns/electron
U=PE_Hilgardite x rElectron Density= 10.30 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Hilgardite is Not Radioactive

Hilgardite Classification

Dana Class:

26.05.14.01 (26)Hydrated Borates Containing Hydroxyl or Halogen

(26.05)Dana Type

(26.05.14)Hilgardite

26.05.14.01 Hilgardite Ca2B5O9Cl•(H2O) P1 1

26.05.14.02 Kurgantaite! CaSr[B5O9]Cl•(H2O) P1 1

26.05.14.03 IMA2007-047! Pb2[B5O9]Cl•0.5H2O Pnn2 mm2

Strunz Class:

06.ED.05 06 - BORATES

06.E - Pentaborates

06.ED -Tecto-pentaborates

06.ED.05 Hilgardite Ca2B5O9Cl•(H2O) P1 1

06.ED.05 Tyretskite Ca2B5O9(OH)•(H2O) P1 1

06.ED.05 Kurgantaite! CaSr[B5O9]Cl•(H2O) P1 1

06.ED.05 IMA2007-047! Pb2[B5O9]Cl•0.5H2O Pnn2 mm2

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 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - Handbook of Mineralogy (MinSocAm)
7 - Handbook of Mineralogy (UofA)
8 - MinDAT
9 - Mineralienatlas (Deutsch)
10 - Online Mineral Museum
11 - QUT Mineral Atlas
12 - Ruff.Info
13 - WWW-MINCRYST

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

Hilgardite

Ca2B5O9Cl•(H2O)
Dana No: 26.05.14.01 Strunz No: 06.ED.05
Locality:

Notes:

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