Gajardoite
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About Gajardoite
Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Lustre:
Vitreous
Hardness:
1½
Specific Gravity:
2.64
Crystal System:
Hexagonal
Isostructural with:
New structure type. Unique combination of elements. Structurally related to torrecillasite. Compare russoite (also As2O3-containing species).
There are two types of layers in the structure: (1) KAs4O6Cl2, built of two neutral As2O3 sheets, with K cations between and Cl cations outside them (lucabindiite has identical layer); (2) edge-sharing sheet built of Ca(H2O)6 trigonal pyramids, with hexagonal cavities occupied by isolated H2O molecules.
There are two types of layers in the structure: (1) KAs4O6Cl2, built of two neutral As2O3 sheets, with K cations between and Cl cations outside them (lucabindiite has identical layer); (2) edge-sharing sheet built of Ca(H2O)6 trigonal pyramids, with hexagonal cavities occupied by isolated H2O molecules.
Classification of Gajardoite
Physical Properties of Gajardoite
Vitreous
Transparency:
Transparent
Streak:
White
Hardness:
1½ on Mohs scale
Comment:
ca. 1.5
Tenacity:
Brittle
Cleavage:
Perfect
{001}
{001}
Fracture:
Irregular/Uneven
Density:
2.64 g/cm3 (Measured) 2.676 g/cm3 (Calculated)
Optical Data of Gajardoite
Type:
Uniaxial (-)
RI values:
nω = 1.780() nε = 1.570(5)
Max Birefringence:
δ = 0.210
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:
High
Chemical Properties of Gajardoite
Formula:
KCa0.5As3+4O6Cl2 · 5H2O
IMA Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Common Impurities:
(Na,Mg)
Crystallography of Gajardoite
Crystal System:
Hexagonal
Class (H-M):
6/mmm (6/m 2/m 2/m) - Dihexagonal Dipyramidal
Space Group:
P6/mmm
Setting:
P6/mmm
Cell Parameters:
a = 5.2558(8) Å, c = 15.967(2) Å
Ratio:
a:c = 1 : 3.038
Unit Cell V:
381.96 ų
Z:
1
Morphology:
Hexagonal plates, up to ca. 100 x 5 μm, forming subparallel rosette-like intergrowths
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 16.00 | (100) |
| 5.31 | (48) |
| 3.466 | (31) |
| 3.013 | (44) |
| 2.624 | (51) |
| 2.353 | (36) |
| 1.845 | (21) |
| 1.460 | (17) |
Type Occurrence of Gajardoite
General Appearance of Type Material:
Hexagonal plates
Place of Conservation of Type Material:
Co-type material is deposited in the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA, catalogue numbers 65585, 65586 and 65587
Associated Minerals at Type Locality:
Synonyms of Gajardoite
Other Information
Notes:
Very slowly soluble in water; slowly soluble in dilute HCl (room temperature).
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 Gajardoite
Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Kampf, A.R., Nash, B., Dini, M. and Molina Donoso, A.A. (2015) Gajardoite, IMA 2015-040. CNMNC Newsletter No. 26, August 2015, page 947; Mineralogical Magazine: 79: 941-947.
Kampf, A.R., Nash, B.P., Dini, M. Molina Donoso, A.A. (2016): Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine: 80: 1265-1272.
Internet Links for Gajardoite
mindat.org URL:
https://www.mindat.org/min-46713.html
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Please feel free to link to this page.
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Localities for Gajardoite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for 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.
Chile (TL) | |
| Kampf, A.R., Nash, B., Dini, M. and Molina Donoso, A.A. (2015) Gajardoite, IMA 2015-040. CNMNC Newsletter No. 26, August 2015, page 947; Mineralogical Magazine, 79, 941-947 ; Kampf, A.R., Nash, B.P., Dini, M. Molina Donoso, A.A. (2016): Gajardoite, KCa0.5As3+4O6Cl2·5H2O, a new mineral related to lucabindiite and torrecillasite from the Torrecillas mine, Iquique Province, Chile. Mineralogical Magazine, 80, 1265-1272. |
Torrecillas mine, Salar Grande, Iquique Province, Tarapacá Region, Chile