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Colourless; colourless ...
Named for Eugene Woldemar Hilgard (1833-1916), German-American geologist, one of the first to describe the Loiuisiana salt dome deposits.
A polytype of Hilgardite

Originally described from Choctaw Salt Dome, Iberville Parish, Louisiana, USA.

Classification of Hilgardite-3Tc URL:
Please feel free to link to this page.

Physical Properties of Hilgardite-3Tc

Diaphaneity (Transparency):
Colourless; colourless in transmitted light
Hardness (Mohs):
On {010} and {100}.

Crystallography of Hilgardite-3Tc

Crystal System:
Class (H-M):
1 - Pedial
Space Group:
Cell Parameters:
a = 11.24Å, b = 22.28Å, c = 6.2Å
α = 90°, β = 90°, γ = 91.2°
a:b:c = 0.504 : 1 : 0.278
Only occurs as oriented intergrowths with hilgardite. The intergrowths are comprised of two partly merged individual crystals of Hilgardite-3Tc, one right-handed and one left-handed, in apparent twin position. These are attached by the positive end of [100] to (100) of a single Hilgardite crystal. Common forms include b, p, t.

Epitaxial Relationships of Hilgardite-3Tc

Epitaxial Minerals:
HilgarditeCa2B5O9Cl · H2O
Epitaxy Comments:
Parahilgardite {100} [001] parallel with Hilgardite {100} [001], with the {010} cleavages of the two minerals inclined at 1°12'.

Optical Data of Hilgardite-3Tc

Biaxial (+)
r > v

Other Names for Hilgardite-3Tc

Name in Other Languages:

Other Information

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-3Tc

Reference List:
Hurlbut (1938) American Mineralogist: 23: 765 (as Parahilgardite).

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 383 (as Parahilgardite).

American Mineralogist (1985): 70: 636-637.

Internet Links for Hilgardite-3Tc

Localities for Hilgardite-3Tc

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.
  • England
    • North Yorkshire
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
  • Louisiana
    • Iberville Parish
      • Plaquemine
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 383, 384; Rocks & Minerals: 69(3): 156-162.; American Mineralogist 23:898
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