Hörnesite (original) (raw)
A valid IMA mineral species - grandfathered
About HörnesiteHide
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Formula:
Mg3(AsO4)2 · 8H2O
Colour:
White; colorless in transmitted light
Lustre:
Sub-Vitreous, Silky, Pearly
Specific Gravity:
2.57 - 2.73
Crystal System:
Monoclinic
Name:
Named by Wilhelm Haidinger in 1860 in honor of Moriz Hörnes, the elder (14 July 1815, Vienna, Austrian Empire - 4 November 1868, Vienna, Austrian Empire), Curator of the Imperial Mineral Cabinet, Vienna, Austria.
Unique IdentifiersHide
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Long-form identifier:
mindat:1:1:1931:2
15520969-29ae-47f0-a120-99048eaf2e11
IMA Classification of HörnesiteHide
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Approved, 'Grandfathered' (first described prior to 1959)
Classification of HörnesiteHide
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8.CE.40
8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
E : With only medium-sized cations, RO4:H2O about 1:2.5
40.3.6.7
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
3 : A3(XO4)2·xH2O
20.2.4
20 : Arsenates (also arsenates with phosphate, but without other anions)
2 : Arsenates of Be, Mg, Ca or Ba
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.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference |
|---|---|---|
| Hns | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Hns | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
Physical Properties of HörnesiteHide
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Sub-Vitreous, Silky, Pearly
Comment:
Luster is pearly on cleavages.
Colour:
White; colorless in transmitted light
Streak:
White to colorless
Cleavage:
Perfect
On {010}, perfect; on {100}, poor.
Density:
2.57 - 2.73 g/cm3 (Measured) 2.57 g/cm3 (Calculated)
Comment:
Density measured on artificial material = 2.609.
Optical Data of HörnesiteHide
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RI values:
_n_α = 1.563 _n_β = 1.571 _n_γ = 1.596
2V:
Measured: 60° , Calculated: 60°
δ = 0.033
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Optical Extinction:
X=b, Z^c = 31°
Pleochroism:
Non-pleochroic
Chemistry of HörnesiteHide
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Mindat Formula:
Mg3(AsO4)2 · 8H2O
Crystallography of HörnesiteHide
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Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 10.262 Å, b = 13.442 Å, c = 4.741 Å
β = 104.9°
Ratio:
a:b:c = 0.763 : 1 : 0.353
Unit Cell V:
631.99 ų (Calculated from Unit Cell)
Morphology:
Crystals prismatic [001] and flattened {010}. Also occurs with a columnar structure; radial-foliated.
X-Ray Powder DiffractionHide
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Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.692 Å | (100) |
| 3.217 Å | (30) |
| 3.005 Å | (50) |
| 2.779 Å | (30) |
| 2.734 Å | (30) |
| 2.712 Å | (50) |
| 1.692 Å | (25) |
Comments:
Also ICDD 35-856 (synthetic)
Geological EnvironmentHide
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Geological Setting:
Oxidized arsenic ore deposits.
On fractures in serpentine.
In marble xenoliths.
Post-mine efflorescence on tunnel walls or dump rocks.
Type Occurrence of HörnesiteHide
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Place of Conservation of Type Material:
Natural History Museum, Vienna, Austria, A.a. 415.
Geological Setting of Type Material:
Oxidized copper-molybdenum deposit.
Associated Minerals at Type Locality:
Synonyms of HörnesiteHide
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Other Language Names for HörnesiteHide
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Relationship of Hörnesite to other SpeciesHide
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Other Members of this group:
Common AssociatesHide
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Associated Minerals Based on Photo Data:
Related Minerals - Strunz-mindat GroupingHide
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Other InformationHide
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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 HörnesiteHide
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References for HörnesiteHide
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Reference List:
Majzlan, Juraj, Reichstein, Anna, Haase, Patrick, Števko, Martin, Sejkora, Jiří, Dachs, Edgar (2024) Thermodynamics of vivianite-group arsenates _M_3(AsO4)2 ⋅ 8H2O (M is Ni, Co, Mg, Zn, Cu) and chemical variability in the natural arsenates of this group. European Journal of Mineralogy, 36 (1) 31-54 doi:10.5194/ejm-36-31-2024
Localities for HörnesiteHide
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This 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.
Locality ListHide
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- 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). 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.