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|Lustre:||Vitreous||Hardness:||5 - 5½|
Hiortdahlite (approved) has been split in 1985 into two species - Hiortdahlite I (not approved as such) and Hiortdahlite II (never submitted to IMA). They are crystallographically close, both belonging to the Wöhlerite Group (Cuspidine Group).
The original hiortdahlite material is from Lille Arøya (Midtre Arøy; Øvre Arøy; Övre-Arö), Langesundsfjorden, Larvik, Vestfold, Norway.
Classification of Hiortdahlite
|IMA status:||Redefined Approved 1985|
|Nickel-Strunz 10th (pending) edition ID:||9.BE.17|
9 : SILICATES (Germanates)
B : Sorosilicates
E : Si2O7 groups, with additional anions; cations in octahedral  and greater coordination
|Dana 8th edition ID:||188.8.131.52|
56 : SOROSILICATES Si2O7 Groups, With Additional O, OH, F and H2O
2 : Si2O7 Groups and O, OH, F, and H2O with cations in  and/or > coordination
|Hey's CIM Ref.:||17.1.22|
17 : Silicates Containing other Anions
1 : Silicates with fluoride (not containing Al)
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Physical Properties of Hiortdahlite
|Hardness (Mohs):||5 - 5½|
Crystallography of Hiortdahlite
|Cell Parameters:||a = 10.95Å, b = 10.31Å, c = 7.29Å|
α = 90.32°, β = 109.03°, γ = 95.08°
|Ratio:||a:b:c = 1.062 : 1 : 0.707|
|Unit Cell Volume:||V 774.45 Å³ (Calculated from Unit Cell)|
Optical Data of Hiortdahlite
|RI values:||nα = 1.639 - 1.658 nβ = 1.643 - 1.664 nγ = 1.646 - 1.671|
|2V:||Measured: 80° , Calculated: 80° to 86°|
|Maximum Birefringence:||δ = 0.007 - 0.013|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Dispersion:||r < v strong|
Chemical Properties of Hiortdahlite
|Simplified for copy/paste:||(Ca,Na)3(Zr,Ti)(Si2O7)(O,OH,F)2|
|Essential elements:||Ca, O, Si, Zr|
|All elements listed in formula:||Ca, F, H, Na, O, Si, Ti, Zr|
Relationship of Hiortdahlite to other Species
|Member of:||Wöhlerite Group|
|Other Members of Group:|
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Hiortdahlite
|Health Warning:||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 Hiortdahlite
Localities for Hiortdahlite
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.
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Locality Updated: Pixley ka Seme District, Northern Cape Province, South AfricaFrom Debbie Woolf, 18th Apr 2014 13:07:50