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Hilgardite-3Tc

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System:TriclinicColour:Colourless; colourless ...
Hardness:5
Name: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

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Physical Properties of Hilgardite-3Tc

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Colourless; colourless in transmitted light
Hardness (Mohs):5
Cleavage:Perfect
On {010} and {100}.

Crystallography of Hilgardite-3Tc

Crystal System:Triclinic
Class (H-M):1 - Pedial
Space Group:P1
Cell Parameters:a = 11.24Å, b = 22.28Å, c = 6.2Å
α = 90°, β = 90°, γ = 91.2°
Ratio:a:b:c = 0.504 : 1 : 0.278
Unit Cell Volume:V 1,552.31 ų (Calculated from Unit Cell)
Z:2
Morphology: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:
Hilgardite
Ca
 
2
B
 
5
O
 
9
Cl · H
 
2
O
Epitaxi 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

Type:Biaxial (+)
Dispersion:r > v

Other Names for Hilgardite-3Tc

Synonyms:
Calciumhilgardite-3TCParahilgardite
Other Languages:
German:Parahilgardit
Russian:Хилгардит-3Tc
Парахильгардит
Simplified Chinese:副氯羟硼钙石
Spanish:Parahilgardita
Traditional Chinese:副氯羥硼鈣石

Other Information

Health Warning: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.

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  • Localities for Hilgardite-3Tc

    The 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. ? 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.
    USA
     
    • 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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