Hilgardite
A valid IMA mineral species - grandfathered
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About Hilgardite
Eugene W. Hilgard
Formula:
Ca2B5O9Cl · H2O
Colour:
Colorless, light pink; colourless in transmitted light
Lustre:
Vitreous
Hardness:
5
Specific Gravity:
2.67 - 2.71
Crystal System:
Triclinic
Member of:
Name:
Named for Eugene Woldemar Hilgard (5 January 1833, Zweibrücken, Rhineland-Palatinate, Germany – 8 January 1916, Berkeley, California, United States), German-American geologist, one of the first to describe the Louisiana salt dome deposits. He is also considered the father of modern soil science in the United States.
Unique Identifiers
Mindat ID:
1902
Long-form identifier:
mindat:1:1:1902:2
GUID
(UUID V4):
(UUID V4):
d6a20d1c-ab9f-47a2-b234-923d1ff109b6
IMA Classification of Hilgardite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1937
Classification of Hilgardite
6.ED.05
6 : BORATES
E : Pentaborates
D : Tekto-pentaborates
6 : BORATES
E : Pentaborates
D : Tekto-pentaborates
Dana 7th ed.:
26.5.14.1
26.5.14.1
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
5 : Pentaborates
26 : HYDRATED BORATES CONTAINING HYDROXYL OR HALOGEN
5 : Pentaborates
10.1.8/9/10
10 : Borates with other anions
1 : Borates with halide
10 : Borates with other anions
1 : Borates with halide
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 |
|---|---|---|
| Hgr | 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 Hilgardite
Vitreous
Transparency:
Transparent
Colour:
Colorless, light pink; colourless in transmitted light
Streak:
White
Hardness:
5 on Mohs scale
Cleavage:
Perfect
Perfect on the {010}, also on {100} but more difficult to realize.
Perfect on the {010}, also on {100} but more difficult to realize.
Fracture:
Conchoidal
Density:
2.67 - 2.71 g/cm3 (Measured) 2.69 g/cm3 (Calculated)
Optical Data of Hilgardite
Type:
Biaxial (+)
RI values:
nα = 1.630 nβ = 1.636 nγ = 1.664
2V:
Measured: 35° , Calculated: 52°
Max Birefringence:
δ = 0.034
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r > v
Chemistry of Hilgardite
Mindat Formula:
Ca2B5O9Cl · H2O
Crystallography of Hilgardite
Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
| Hilgardite-1Tc | Hilgardite-3Tc | Hilgardite-4M |
|---|---|---|
| Triclinic | Monoclinic | |
| 1 - Pedial | m - Domatic | |
| P1 | ||
| a = 11.24 Å, b = 22.28 Å, c = 6.2 Å α = 90°, β = 90°, γ = 91.2° | a = 11.470(3) Å, b = 11.321(4) Å, c = 6.321(5) Å β = 90.02(7)° | |
| a:b:c = 0.504 : 1 : 0.278 | a:b:c = 1.013 : 1 : 0.558 | |
| V 1,552.31 ų (Calculated from Unit Cell) | V 820.79 ų (Calculated from Unit Cell) | |
| 2 |
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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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) |
|---|---|---|---|---|---|---|---|
| 0000696 | Hilgardite | Ghose S, Wan C (1979) Hilgardite, Ca2[B5O9]Cl*H2O: a piezoelectric zeolite-type pentaborate American Mineralogist 64 187-195 |  | 1979 | Choctow Salt Dome, Iberville Parish, Louisiana, USA | 0 | 293 |
| 0000901 | Hilgardite | Wan C, Ghose S (1983) Parahilgardite, Ca6[B5O9]3Cl3*3H2O: a triclinic piezoelectric zeolite-type pentaborate American Mineralogist 68 604-613 | | 1983 | Iberville Parish, Louisiana, USA | 0 | 293 |
| 0010290 | Hilgardite | Burns P C, Hawthorne F C (1994) Refinement of the structure of hilgardite-1A Acta Crystallographica C50 653-655 |  | 1994 | Penobsquis potash deposit, Sussex, New Brunswick | 0 | 293 |
| 0015604 | Hilgardite | Rumanova I M, Iorysh Z I, Belov N V (1977) Crystal structure of triclinic chilgardite Ca2[B5O9]Cl*H2O = Ca2[B3+-B2deltaO9]Cl*H2O Soviet Physics Doklady 22 460-462 | 1977 | not given | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| - Å | () |
Comments:
X-ray powder diffraction data can be found on the polytype pages.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
Marine evaporite deposits
Type Occurrence of Hilgardite
Place of Conservation of Type Material:
Harvard University, Cambridge, Massachusetts, USA, 100899, 100947, 106583.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, R7822.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, R7822.
Geological Setting of Type Material:
Salt dome.
Associated Minerals at Type Locality:
Reference:
Hurlbut, C.S., Taylor, R.E. (1937) Hilgardite, a new mineral species from Choctaw Salt Dome, Louisiana. American Mineralogist: 22: 1052-1057.
Synonyms of Hilgardite
Other Language Names for Hilgardite
German:Hilgardit
Russian:Хилгардит
Simplified Chinese:氯羟硼钙石
Spanish:Hilgardita
Traditional Chinese:氯羥硼鈣石
Varieties of Hilgardite
| Strontiohilgardite | |
| Strontiohilgardite-1Tc | A strontium-bearing (strontian) hilgardite-1Tc. |
Relationship of Hilgardite to other Species
Member of:
Other Members of this group:
| Kurgantaite | CaSr[B5O9]Cl · H2O | Tric. 1 : P1 |
| Leucostaurite | Pb2[B5O9]Cl · 0.5H2O | Orth. mm2 : Pnn2 |
| Tyretskite | Ca2B5O9OH · H2O | Tric. 1 : P1 |
Common Associates
Associated Minerals Based on Photo Data:
| 63 photos of Hilgardite associated with Boracite | Mg3(B7O13)Cl |
| 16 photos of Hilgardite associated with Volkovskite | KCa4[B5O8OH]4[B(OH)3]2Cl · 4H2O |
| 4 photos of Hilgardite associated with Hilgardite-3Tc | |
| 2 photos of Hilgardite associated with Sylvite | KCl |
| 1 photo of Hilgardite associated with Magnesite | MgCO3 |
Related Minerals - Strunz-mindat Grouping
| 6.ED.05 | Tyretskite | Ca2B5O9OH · H2O |
| 6.ED.05 | Kurgantaite | CaSr[B5O9]Cl · H2O |
Other Information
Electrical:
Piezoelectric
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 Hilgardite
mindat.org URL:
https://www.mindat.org/min-1902.html
Please feel free to link to this page.
Please feel free to link to this page.
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Mineral Dealers:
References for Hilgardite
Reference List:
Dunn, Pete J., Grice, Joel D. Fleischer, Michael, Pabst, Adolf (1984) New mineral names. American Mineralogist, 69 (1-2) 210-215
Rachlin, Alan L., Mandarino, Joseph A., Murowchick, Bernard L., Ramik, Robert A., Dunn, Pete J., Back, Malcolm E. (1986) Mineralogy of hilgardite-4M from evaporites in New Brunswick. The Canadian Mineralogist, 24 (4) 689-693
Localities for Hilgardite
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.
Canada | |
| Grice et al. (1996) +1 other reference |
| Roulston et al. (1981) +1 other reference |
| Grice et al. (2005) |
China | |
| [Hilgardite-3Tc] Li et al. (2015) |
Germany | |
| Clark (1993) |
Israel | |
| Anthony (2003) |
Kazakhstan | |
| Pekov (1998) +2 other references |
| Pekov et al. (1993) +2 other references |
Russia | |
| Dimitri Belakovski |
| Mazurov et al. (2007) |
Turkey | |
| [Hilgardite-4M] Koçak et al. (2016) +1 other reference |
UK | |
| BMS Collection hilgardite-1TC +2 other references |
| Smith et al. (2014) |
| Smith et al. (2014) | |
| Kemp et al. (2016) | |
USA | |
| Rocks & Min.: 64:472. +1 other reference |
| American Mineralogist 23:898 +1 other reference |
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Boulby Mine, Loftus, Redcar and Cleveland, North Yorkshire, England, UK