Gajardoite
A valid IMA mineral species
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About Gajardoite
Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Lustre:
Vitreous
Hardness:
1½
Specific Gravity:
2.64
Crystal System:
Hexagonal
Member of:
Name:
Named in honor of Aníbal Gajardo Cubillos (b. 1945), Chilean geologist. He has more than 200 publications, especially on the non-metallic mineral deposits of Chile. He has held several leadership positions in SERNAGEOMIN, Chile’s National Geology and Mining Service, and was professor in the Department of Geology, University of Chile from 1979 to 2009. He was also President of the Association of Geologists of Chile. Pronounced /ga:′ha:r dOu ait/.
Isostructural with:
New structure type. The K analogue of gajardoite-(NH4). Unique combination of elements (at the upload time). 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.
Unique Identifiers
Mindat ID:
46713
Long-form identifier:
mindat:1:1:46713:1
Similar Names
| Gajardoite-(NH4) | A valid IMA mineral species | (NH4)As43+O6Cl2(Ca0.5◻0.5)(H2O)5 |
IMA Classification of Gajardoite
Classification of Gajardoite
3.DC.
3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Gaj | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
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(3) nε = 1.570(5)
Max. Birefringence:
δ = 0.210
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate
Chemistry of Gajardoite
Mindat Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Element Weights:
Common Impurities:
(Na,Mg)
Crystallography of Gajardoite
Crystal System:
Hexagonal
Class (H-M):
6/mmm(6/m2/m2/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 Å | (100) |
| 5.31 Å | (48) |
| 3.466 Å | (31) |
| 3.013 Å | (44) |
| 2.624 Å | (51) |
| 2.353 Å | (36) |
| 1.845 Å | (21) |
| 1.460 Å | (17) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] | |
| 47g : [Halogen-bearing surface weathering minerals] |
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 Language Names for Gajardoite
Dutch:Gajardoiet
German:Gajardoit
Relationship of Gajardoite to other Species
Member of:
Other Members of Lucabindiite Group:
| Cuatrocapaite-(K) | K3(NaMg◻)(As2O3)6Cl6 · 16H2O | Trig. 3m(32/m) : R3m |
| Cuatrocapaite-(NH4) | (NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2O | Trig. 3m(32/m) : R3m |
| Ermakovite | (NH4)(As2O3)2Br | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Gajardoite-(NH4) | (NH4)As3+4O6Cl2(Ca0.5◻0.5)(H2O)5 | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Lucabindiite | (K,NH4)As4O6(Cl,Br) | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Mauriziodiniite | (NH4)(As2O3)2I | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Russoite | (NH4)ClAs2O3(H2O)0.5 | Hex. 622 : P622 |
| Torrecillasite | Na(As,Sb)3+4O6Cl | Orth. |
Related Minerals - Strunz-mindat Grouping
| 3.DC. | Lucabindiite | (K,NH4)As4O6(Cl,Br) |
| 3.DC. | Cuatrocapaite-(NH4) | (NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2O |
| 3.DC. | Cuatrocapaite-(K) | K3(NaMg◻)(As2O3)6Cl6 · 16H2O |
| 3.DC. | Napoliite | Pb2OFCl |
| 3.DC. | Torrecillasite | Na(As,Sb)3+4O6Cl |
| 3.DC.05 | Paralaurionite | PbCl(OH) |
| 3.DC.05 | Laurionite | PbCl(OH) |
| 3.DC.05 | Mauriziodiniite | (NH4)(As2O3)2I |
| 3.DC.05 | Russoite | (NH4)ClAs2O3(H2O)0.5 |
| 3.DC.10 | Fiedlerite | Pb3FCl4(OH) · H2O |
| 3.DC.15 | Penfieldite | Pb2Cl3(OH) |
| 3.DC.15 | Telluroperite | Pb3TeO4Cl2 |
| 3.DC.20 | Laurelite | Pb7F12Cl2 |
| 3.DC.25 | Zhangpeishanite | BaFCl |
| 3.DC.25 | Matlockite | PbFCl |
| 3.DC.25 | Zavaritskite | (BiO)F |
| 3.DC.25 | Rorisite | CaFCl |
| 3.DC.25 | Bismoclite | BiOCl |
| 3.DC.25 | Vegrandisite | BaCl2 |
| 3.DC.30 | Nadorite | PbSbClO2 |
| 3.DC.30 | Perite | PbBiClO2 |
| 3.DC.40 | Thorikosite | Pb3Cl2(OH)(SbO3,AsO3) |
| 3.DC.45 | Mereheadite | Pb47Cl25(OH)13O24(CO3)(BO3)2 |
| 3.DC.50 | Blixite | Pb8O5(OH)2Cl4 |
| 3.DC.52 | Rumseyite | Pb2OClF |
| 3.DC.55 | Vladkrivovichevite | [Pb32O18][Pb4Mn2O]Cl14(BO3)8 · 2H2O |
| 3.DC.55 | Pinalite | Pb3WO5Cl2 |
| 3.DC.57 | Yeomanite | Pb2O(OH)Cl |
| 3.DC.60 | Symesite | Pb10(SO4)O7Cl4 · H2O |
| 3.DC.60 | 'Lorettoite' | Pb7O6Cl2 |
| 3.DC.62 | 'Sarawakite (of Frenzel)' | Sb, O, Cl (?) |
| 3.DC.65 | Ecdemite | Pb6As3+2O7Cl4 |
| 3.DC.70 | Mendipite | Pb3Cl2O2 |
| 3.DC.75 | Damaraite | Pb3Cl(OH)O2 |
| 3.DC.80 | Onoratoite | Sb8Cl2O11 |
| 3.DC.95 | Barstowite | Pb4Cl6(CO3) · H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 6.3492% | 1,968 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
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.
Internet Links for Gajardoite
mindat.org URL:
https://www.mindat.org/min-46713.html
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References for Gajardoite
Reference List:
Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2015) New minerals and nomenclature modifications approved in 2015, CNMNC Newsletter 26. Mineralogical Magazine, 79 (4) 941-947 doi:10.1180/minmag.2015.079.4.05
Kampf, Anthony R., Nash, Barbara P., Dini, Maurizio, Donoso, Arturo Molina 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 (7) 1265-1272 doi:10.1180/minmag.2016.080.065
Localities for Gajardoite
Showing 1 localities.
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.
Chile (TL) | |
| Hålenius et al. (2015) +1 other reference |
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Torrecillas mine, Iquique, Iquique Province, Tarapacá, Chile