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Hilgardite

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Eugene Woldemar Hilgard
Formula:
Ca2B5O9Cl · H2O
System:
Triclinic
Colour:
Colorless, light pink; ...
Hardness:
5
Name:
Named for Eugene Woldemar Hilgard (1833-1916), German-American geologist, one of the first to describe the Louisiana salt dome deposits.
Hilgardite Group.

Several polytypes are known, as well as Sr-bearing varieties.


Classification of Hilgardite

Approved, 'Grandfathered' (first described prior to 1959)
6.ED.05

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
10.1.8/9/10

10 : Borates with other anions
1 : Borates with halide

Occurrences of Hilgardite

Type Occurrence of Hilgardite

Geological Setting of Type Material:
Salt dome.

Physical Properties of Hilgardite

Vitreous
Diaphaneity (Transparency):
Transparent
Colour:
Colorless, light pink; colourless in transmitted light
Streak:
White
Hardness (Mohs):
5
Cleavage:
Perfect
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)

Crystallography of Hilgardite

Polytype:
Formula:
Crystal System:
Class (H-M)
Space Group:
Space Group Setting:
Cell Parameters:
Ratio:
Unit Cell Volume (calc):
Z:
Hilgardite-1TcHilgardite-3TcHilgardite-4M
   
 Triclinic Monoclinic 
1 - Pedialm - Domatic
 P1 
   

a = 11.24Å, b = 22.28Å, c = 6.2Å
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 : 0.278a: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 

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.
Surface Relief:
Moderate
Dispersion:
r > v

Chemical Properties of Hilgardite

Formula:
Ca2B5O9Cl · H2O
All elements listed in formula:

Relationship of Hilgardite to other Species

Other Members of Group:
KurgantaiteCaSr[B5O9]Cl · H2O
LeucostauritePb2[B5O9]Cl · 0.5H2O
TyretskiteCa2B5O9OH · H2O
6.ED.05TyretskiteCa2B5O9OH · H2O
6.ED.05KurgantaiteCaSr[B5O9]Cl · H2O
10.1.1TeepleiteNa2[B(OH)4]Cl
10.1.2BandyliteCu[B(OH)4]Cl
10.1.3BerboriteBe2(BO3)(OH,F) · H2O
10.1.4FluoboriteMg3(BO3)(F,OH)3
10.1.5BoraciteMg3(B7O13)Cl
10.1.6KarliteMg7(BO3)3(OH,Cl)5
10.1.7ShabyniteMg5(BO3)(OH)5(Cl,OH)2 · 4H2O
10.1.11SolongoiteCa2(H3B3O7)(OH)Cl
10.1.12HydrochlorboriteCa4B8O15Cl2 · 21H2O
10.1.13EkateriniteCa2(B4O7)(Cl,OH)2 · 2H2O
10.1.14VolkovskiteKCa4[B5O8OH]4[B(OH)3]2Cl · 4H2O
10.1.15ChelkariteCaMgB2O4(Cl,OH)2 · 5H2O Or near, with Cl:OH = 3:1
10.1.16JohachidoliteCaAlB3O7
10.1.17SatimoliteKNa2Al4[Cl|B2O5]3 · 13H2O
10.1.18ChambersiteMn32+(B7O13)Cl
10.1.19Congolite(Fe2+,Mg)3(B7O13)Cl
10.1.20EricaiteFe32+(B7O13)Cl

Other Names for Hilgardite

Name in Other Languages:
German:Hilgardit
Simplified Chinese:氯羟硼钙石
Spanish:Hilgardita
Traditional Chinese:氯羥硼鈣石

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.

References for Hilgardite

Reference List:
Hurlbut, C. S. & Taylor, R. E. (1937): Hilgardite, a new mineral species from Choctaw Salt Dome, Louisiana. American Mineralogist. 22, 1052-1057.

Taylor (1937): Bulletin of the American Association of Petr. Geol. 21: 1268.

American Mineralogist .(1938): 23: 765-771.

Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124pp.: 382-383.

Braitsch, O. (1959) 1Tc-Strontiohilgardite (Ca,Sr)2[B5O9](OH)2Cl and seine Stellung in the Hilgarditgruppe. Beiträge Mineral. und Petrogr.: 6: 233-247. [Abs. in Am. Mineral. 44, 1102: http://www.minsocam.org/ammin/AM44/AM44_1102.pdf]

American Mineralogist (1984): 69: 214.

Ghose, S. (1985) A new nomenclature for the borate minerals in the hilgardite (Ca2B5O9Cl·H2O)-tyretskite (Ca2B5O9OH·H2O) group. American Mineralogist (1985): 70: 636-637.

Rachlin, A.L., Mandarino, J.., Murowchick, B.L., Ramik, R.A., Dunn, P.J., and Bac, M.E. (1986) Mineralogy of hilgardite-4M from evaporites in New Brunswick. Canadian Mneralogist: 24: 689-693.

Burns, P.C. and Hawthorne, F.C. (1994) Refinement of the structure of hilgardite-1A. Acta Crystallographica: C50: 653-655.

Grew, E.S., and Anovitz, L.M. (1996) BORON: Mineralogy, Petrology and Geochemistry, second edition, as revised (2002).

Internet Links for Hilgardite

mindat.org URL:
http://www.mindat.org/min-1902.html
Please feel free to link to this page.
Specimens:
The following Hilgardite specimens are currently listed for sale on minfind.com.

Localities for Hilgardite

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.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
Canada
 
  • New Brunswick
    • Kings Co.
      • Cardwell Parish
        • Penobsquis
Canadian Mineralogist (1996): 34: 657-665.; Canadian Mineralogist (1996): 34: 881-892
      • Hammond Parish
        • Salt Springs evaporite deposit
P.C. Burns, F.C. Hawthorne, J.A.R. Stirling: Can. Mineral. 30:445-448 (1992); Roulston, B.V. and Waugh, D.C.E. (1981) A borate mineal assemblage from the Penobsquis and Salt Springs evaporite deposits of southern New Brunswick. Canadian Mineralogist: 19: 291-301.
      • Studholm Parish
Canadian Mineralogist: 43: 1469-1487.
China
 
  • Yunnan Province
    • Pu'er Prefecture
      • Jiangcheng Co.
[Hilgardite-3Tc] Li, M., Yan, M., Wang, Z., Liu, X., Fang, X., & Li, J. (2015). The origins of the Mengye potash deposit in the Lanping–Simao Basin, Yunnan Province, Western China. Ore Geology Reviews, 69, 174-186.
Germany
 
  • Lower Saxony
    • Göttingen
      • Reyershausen
[Clark, 1993 - "Hey's Mineral Index"]
Israel
 
  • Southern District (HaDarom District)
Anthony, et al (2003) Handbook of Mineralogy, Vol. 5, p. 288.
Kazakhstan
 
  • Aktobe Province (Aqtöbe Oblysy; Aktubinskaya Oblast')
    • Aksai Valley
Pekov, I. (1998) Minerals First discovered on the territory of the former Soviet Union 369p. Ocean Pictures, Moscow; ERCOSPAN (2011) Independent Geological Report on the Zhilianskoe and Chelkar Potash Deposits in Kazakhstan EGB 11-012
  • Atyrau Province (Atyrau Oblysy; Atyrau Oblast')
    • Atyrau (Gur'yev)
Pekov, I. (1998) Minerals First discovered on the territory of the former Soviet Union 369p. Ocean Pictures, Moscow; Evseev, A. A. (1995) Kazaknstan and Middle Asia. A brief Mineralogical Guide. World of Stone 8:24-30; Pekov, I. V. & Abramov, D. V. (1993): Boron deposit of the Inder and its minerals. World of Stones, 1, 23-30.
Russia
 
  • Eastern-Siberian Region
    • Prebaikalia (Pribaikal'e)
      • Irkutskaya Oblast'
        • Lena-Angara salt Basin
Dimitri Belakovski
        • Zheleznogorsk
Mazurov, M.P., Grishina, S.N., Istomin, V.E., and Titov, A.T. (2007): Geology of Ore Deposits 49(4), 271-284.
Turkey
 
  • Central Anatolia Region
    • Eskişehir Province
      • Kirka
[Hilgardite-4M] Koçak, İ. & Koç, Ş. (2016): Geochemical characteristics of Kırka (Sarıkaya) borate deposit, northwestern Anatolia, Turkey. Journal of Earth System Science: 125: 147-164; http://forum.amiminerals.it/viewtopic.php?f=5&t=12548 (2016)
UK
 
  • England
    • North Yorkshire
      • Loftus
BMS Collection hilgardite-1TC; UK Journal of Mines and Minerals, No. 14 p4-7
Smith, F.W., Dearlove, J.P.L., Kemp, S.J., Bell, C.P., Milne, C.J. and Pottas, T.L. (2014) Potash – Recent exploration developments in North Yorkshire. Pp. 45-50 in Hunger, E., Brown, T. J. and Lucas, G. (Eds.) Proceedings of the 17th Extractive Industry Geology Conference, EIG Conferences Ltd. 202pp
Smith, F.W., Dearlove, J.P.L., Kemp, S.J., Bell, C.P., Milne, C.J. and Pottas, T.L. (2014) Potash – Recent exploration developments in North Yorkshire. Pp. 45-50 in Hunger, E., Brown, T. J. and Lucas, G. (Eds.) Proceedings of the 17th Extractive Industry Geology Conference, EIG Conferences Ltd. 202pp
USA
 
  • Alabama
    • Clarke Co.
Rocks & Min.: 64:472.
  • Louisiana
    • Iberville Parish
      • Plaquemine
Hurlbut, C. S., Taylor, R. E. (1937): Hilgardite, a new mineral species from Choctaw Salt Dome, Louisiana. American Mineralogist. 22, 1052-1057; American Mineralogist 23:898
Mineral and/or Locality  
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