Hilgardite-3Tc
A structural variant of Hilgardite
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About Hilgardite-3Tc
Eugene W. Hilgard
Formula:
Ca2B5O9Cl · H2O
Colour:
Colourless; colourless in transmitted light
Lustre:
Vitreous
Hardness:
5
Crystal System:
Triclinic
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.
A polytype of Hilgardite
Triclinic polytype of Hilgardite.
Originally described from Choctaw Salt Dome, Iberville Parish, Louisiana, USA.
Triclinic polytype of Hilgardite.
Originally described from Choctaw Salt Dome, Iberville Parish, Louisiana, USA.
Unique Identifiers
Mindat ID:
9762
Long-form identifier:
mindat:1:1:9762:4
Physical Properties of Hilgardite-3Tc
Vitreous
Transparency:
Transparent
Colour:
Colourless; colourless in transmitted light
Hardness:
5 on Mohs scale
Cleavage:
Perfect
On {010} and {100}.
On {010} and {100}.
Optical Data of Hilgardite-3Tc
Type:
Biaxial (+)
Dispersion:
r > v
Chemistry of Hilgardite-3Tc
Mindat Formula:
Ca2B5O9Cl · H2O
Element Weights:
Crystallography of Hilgardite-3Tc
Crystal System:
Triclinic
Class (H-M):
1 - Pedial
Space Group:
P1
Cell Parameters:
a = 11.24 Å, b = 22.28 Å, c = 6.2 Å
α = 90°, β = 90°, γ = 91.2°
α = 90°, β = 90°, γ = 91.2°
Ratio:
a:b:c = 0.504 : 1 : 0.278
Unit Cell 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 | Ca2B5O9Cl · H2O |
Epitaxy Comments:
Parahilgardite {100} [001] parallel with Hilgardite {100} [001], with the {010} cleavages of the two minerals inclined at 1°12'.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.87 Å | (100) |
| 2.83 Å | (100) |
| 2.755 Å | (80) |
| 2.12 Å | (80) |
| 2.033 Å | (80) |
| 5.7 Å | (60) |
| 3.14 Å | (60) |
Comments:
Choctaw salt dome, Louisiana, USA.
Synonyms of Hilgardite-3Tc
Other Language Names for Hilgardite-3Tc
German:Parahilgardit
Russian:Хилгардит-3Tc
Парахильгардит
Парахильгардит
Simplified Chinese:副氯羟硼钙石
Spanish:Parahilgardita
Traditional Chinese:副氯羥硼鈣石
Common Associates
Associated Minerals Based on Photo Data:
| 4 photos of Hilgardite-3Tc associated with Hilgardite | Ca2B5O9Cl · H2O |
| 4 photos of Hilgardite-3Tc associated with Boracite | Mg3(B7O13)Cl |
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.
Internet Links for Hilgardite-3Tc
mindat.org URL:
https://www.mindat.org/min-9762.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Hilgardite-3Tc
Reference List:
Localities for Hilgardite-3Tc
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.
China | |
| Li et al. (2015) |
UK | |
| Milne (1978) |
| Smith et al. (2014) |
USA | |
| Rocks & Minerals: 69 (3) +2 other references |
Choctaw Salt Dome, Plaquemine, Iberville Parish, Louisiana, USA