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⇱ Gajardoite: Mineral information, data and localities.

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Gajardoite

A valid IMA mineral species
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About GajardoiteHide

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Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Lustre:
Vitreous
Hardness:
1½
Specific Gravity:
2.64
Crystal System:
Hexagonal
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.


Unique IdentifiersHide

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Mindat ID:
46713
Long-form identifier:
mindat:1:1:46713:1

Similar NamesHide

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Gajardoite-(NH4)A valid IMA mineral species(NH4)As43+O6Cl2(Ca0.5◻0.5)(H2O)5

IMA Classification of GajardoiteHide

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Approved
IMA Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Approval year:
2015
First published:
2016

Classification of GajardoiteHide

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3.DC.

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
GajIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of GajardoiteHide

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Vitreous
Transparency:
Transparent
Streak:
White
Hardness:
1½ on Mohs scale
Comment:
ca. 1.5
Tenacity:
Brittle
Cleavage:
Perfect
{001}
Fracture:
Irregular/Uneven
Density:
2.64 g/cm3 (Measured)    2.676 g/cm3 (Calculated)

Optical Data of GajardoiteHide

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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.

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.

Surface Relief:
Moderate

Chemistry of GajardoiteHide

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Mindat Formula:
KCa0.5As3+4O6Cl2 · 5H2O
Element Weights:
Element% weight
As48.666 %
O28.580 %
Cl11.514 %
K6.349 %
Ca3.254 %
H1.637 %

Calculated from ideal end-member formula.
Common Impurities:
(Na,Mg)

Crystallography of GajardoiteHide

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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 DiffractionHide

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Powder Diffraction Data:
d-spacingIntensity
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 EnvironmentHide

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Paragenetic Mode(s):

Type Occurrence of GajardoiteHide

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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 GajardoiteHide

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Other Language Names for GajardoiteHide

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German:Gajardoit

Relationship of Gajardoite to other SpeciesHide

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Other Members of Lucabindiite Group:
Cuatrocapaite-(K)K3(NaMg◻)(As2O3)6Cl6 · 16H2OTrig. 3m(32/m) : R3m
Cuatrocapaite-(NH4)(NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2OTrig. 3m(32/m) : R3m
Ermakovite(NH4)(As2O3)2BrHex. 6/mmm(6/m2/m2/m) : P6/mmm
Gajardoite-(NH4)(NH4)As3+4O6Cl2(Ca0.5◻0.5)(H2O)5Hex. 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)2IHex. 6/mmm(6/m2/m2/m) : P6/mmm
Russoite(NH4)ClAs2O3(H2O)0.5Hex. 622 : P622
TorrecillasiteNa(As,Sb)3+4O6ClOrth.

Related Minerals - Strunz-mindat GroupingHide

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3.DC.Lucabindiite(K,NH4)As4O6(Cl,Br)Hex. 6/mmm(6/m2/m2/m) : P6/mmm
3.DC.Cuatrocapaite-(NH4)(NH4)3(NaMg◻)(As2O3)6Cl6 · 16H2OTrig. 3m(32/m) : R3m
3.DC.Cuatrocapaite-(K)K3(NaMg◻)(As2O3)6Cl6 · 16H2OTrig. 3m(32/m) : R3m
3.DC.NapoliitePb2OFClTet. 4/mmm(4/m2/m2/m) : P42/mcm
3.DC.TorrecillasiteNa(As,Sb)3+4O6ClOrth.
3.DC.05ParalaurionitePbCl(OH)Mon. 2/m : B2/m
3.DC.05LaurionitePbCl(OH)Orth. mmm(2/m2/m2/m)
3.DC.05Mauriziodiniite(NH4)(As2O3)2IHex. 6/mmm(6/m2/m2/m) : P6/mmm
3.DC.05Russoite(NH4)ClAs2O3(H2O)0.5Hex. 622 : P622
3.DC.10FiedleritePb3FCl4(OH) · H2OMon. 2/m
3.DC.15PenfielditePb2Cl3(OH)Hex. 6 : P6
3.DC.15TelluroperitePb3TeO4Cl2Orth. mmm(2/m2/m2/m)
3.DC.20LaurelitePb7F12Cl2Hex. 6 : P6
3.DC.25ZhangpeishaniteBaFClTet. 4/mmm(4/m2/m2/m) : P4/nmm
3.DC.25MatlockitePbFClTet. 4/mmm(4/m2/m2/m) : P4/nmm
3.DC.25Zavaritskite(BiO)FTet. 4/mmm(4/m2/m2/m) : P4/nmm
3.DC.25RorisiteCaFClTet. 4/mmm(4/m2/m2/m) : P4/nmm
3.DC.25BismocliteBiOClTet. 4/mmm(4/m2/m2/m) : P4/nmm
3.DC.25VegrandisiteBaCl2Orth. mmm(2/m2/m2/m) : Pnma
3.DC.30NadoritePbSbClO2Orth. mmm(2/m2/m2/m) : Cmcm
3.DC.30PeritePbBiClO2Orth. mmm(2/m2/m2/m) : Cmcm
3.DC.40ThorikositePb3Cl2(OH)(SbO3,AsO3)Tet. 4/mmm(4/m2/m2/m) : I4/mmm
3.DC.45MereheaditePb47Cl25(OH)13O24(CO3)(BO3)2Mon. m
3.DC.50BlixitePb8O5(OH)2Cl4Orth.
3.DC.52RumseyitePb2OClF Tet. 4/mmm(4/m2/m2/m) : I4/mmm
3.DC.55Vladkrivovichevite[Pb32O18][Pb4Mn2O]Cl14(BO3)8 · 2H2O Orth. mmm(2/m2/m2/m) : Pmmn
3.DC.55PinalitePb3WO5Cl2Orth. mmm(2/m2/m2/m)
3.DC.57YeomanitePb2O(OH)ClOrth. mmm(2/m2/m2/m) : Pnma
3.DC.60SymesitePb10(SO4)O7Cl4 · H2OTric. 1 : P1
3.DC.60'Lorettoite'Pb7O6Cl2Orth.
3.DC.62'Sarawakite (of Frenzel)'Sb, O, Cl (?)
3.DC.65EcdemitePb6As3+2O7Cl4Mon. 2 : P21
3.DC.70MendipitePb3Cl2O2Orth. 222 : P212121
3.DC.75DamaraitePb3Cl(OH)O2Orth. mm2 : Pmc21
3.DC.80OnoratoiteSb8Cl2O11Tric. 1 : P1
3.DC.95BarstowitePb4Cl6(CO3) · H2OMon. 2/m : P21/m

RadioactivityHide

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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: –

DistanceDose rateRisk
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 InformationHide

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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 GajardoiteHide

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mindat.org URL:
https://www.mindat.org/min-46713.html
Please feel free to link to this page.

References for GajardoiteHide

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Localities for GajardoiteHide

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Showing 1 localities.

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the 👁 Image
symbol to view information about a locality. The 👁 Image
symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

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👁 Image
- This locality has map coordinates listed. 👁 Image
- This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. 👁 Image
- Good crystals or important locality for species. 👁 Image
- World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Chile (TL)
  • Tarapacá
    • Iquique Province
      • Iquique
Hålenius et al. (2015) +1 other reference
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