Prachařite
A valid IMA mineral species
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Dr. Ivan Prachař of Prague, Czech Republic.
Formula:
CaSb5+2(As3+2O5)2O2 · 10H2O
Colour:
Colorless to white
Lustre:
Vitreous
Hardness:
2 - 2½
Specific Gravity:
2.838 (Calculated)
Crystal System:
Trigonal
Name:
In honour of Dr. Ivan Prachař of Prague, Czech Republic, who studied and documented the mineralogy and underground workings of the famous Lavrion mining district over more than 20 years.
New structure type; details:
* basis: two different layers, with:
* 6-membered ring of corner-sharing SbO6 octahedra;
* Ca1 atom in the centre of the ring (C.N. = 8);
* (As2O5)4− diarsenite group resulting from corner-sharing of two non-equivalent AsO3 groups;
* interlayer Ca2 atom (C.N. = 7) and three water molecules (one of them is in a split position, i.e., partially occupied site).
* basis: two different layers, with:
* 6-membered ring of corner-sharing SbO6 octahedra;
* Ca1 atom in the centre of the ring (C.N. = 8);
* (As2O5)4− diarsenite group resulting from corner-sharing of two non-equivalent AsO3 groups;
* interlayer Ca2 atom (C.N. = 7) and three water molecules (one of them is in a split position, i.e., partially occupied site).
Unique Identifiers
Mindat ID:
53208
Long-form identifier:
mindat:1:1:53208:2
GUID
(UUID V4):
(UUID V4):
62bfac39-865e-4358-bcbf-7544b7442ba8
IMA Classification of Prachařite
Approved
Approval year:
2018
Classification of Prachařite
4.JD.20
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
J : Arsenites, antimonites, bismuthites, sulfites, selenites, tellurites; iodates
D : Arsenites, antimonites, bismuthites; with additional anions, with H2O
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
J : Arsenites, antimonites, bismuthites, sulfites, selenites, tellurites; iodates
D : Arsenites, antimonites, bismuthites; with additional anions, with H2O
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 |
|---|---|---|
| Pcř | 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 Prachařite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Colorless to white
Hardness:
2 - 2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
good cleavage parallel to {0001} and a distinct cleavage parallel to {1010}.
good cleavage parallel to {0001} and a distinct cleavage parallel to {1010}.
Fracture:
Irregular/Uneven
Density:
2.838 g/cm3 (Calculated)
Optical Data of Prachařite
Type:
Uniaxial (-)
RI values:
nω = 1.619(1) nε = 1.553(1)
Max Birefringence:
δ = 0.066
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:
Moderate
Pleochroism:
Non-pleochroic
Chemistry of Prachařite
Mindat Formula:
CaSb5+2(As3+2O5)2O2 · 10H2O
Chemical Analysis
Oxide wt%:
| 1 | |
|---|---|
| CaO | 6.28/7.12 % |
| MgO | 0.09/- % |
| ZnO | -/0.01 % |
| Sb2O5 | 39.22/40.19 % |
| As2O3 | 47.59/47.39 % |
| SO3 | -/0.02 % |
| H2O | 21.65/22.04 % |
| Total: | 114.83 % |
Empirical formulas:
| Sample ID | Empirical Formula |
|---|---|
| 1 | (1) (Ca0.93Mg0.02)?0.95Sb2.02(AsO3)4.00·10H2O; (2) Ca1.04Sb2.03(AsO3)3.92·10H2O |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Plaka Mine No. 80, Plaka Mines, Plaka, Lavrion mining district, Lavreotiki, East Attica, Attica, Greece | by EPMA (WDS), two datasets; empirical formula basis: O = 22 atoms per formula unit; water content derived from ideal composition (via crystal-structure determination); elevated total due to loss of 1/3 of water molecules as induced by electron beam |
Crystallography of Prachařite
Crystal System:
Trigonal
Class (H-M):
3m (3 2/m) - Hexagonal Scalenohedral
Space Group:
P3c1
Setting:
P3c1
Cell Parameters:
a = 13.951(2) Å, c = 19.899(2) Å
Ratio:
a:c = 1 : 1.426
Unit Cell V:
3,354.07 ų (Calculated from Unit Cell)
Z:
6
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.96 Å | (100) |
| 6.05 Å | (33) |
| 5.16 Å | (30) |
| 3.314 Å | (59) |
| 2.994 Å | (95) |
| 2.570 Å | (31) |
| 1.717 Å | (30) |
| 1.593 Å | (26) |
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] |
Type Occurrence of Prachařite
General Appearance of Type Material:
Colorless to white thin tabular hexagonal crystals.
Place of Conservation of Type Material:
Cotype material is deposited in the mineralogical collections of the Natural History Museum, Vienna, Austria, catalogue no. O 357, the National Museum, Prague, Czech Republic, catalogue no. P1P 15/2018, and the Natural History Museum of Los Angeles County
Associated Minerals at Type Locality:
Synonyms of Prachařite
Related Minerals - Strunz-mindat Grouping
Fluorescence of Prachařite
none
Other Information
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 Prachařite
mindat.org URL:
https://www.mindat.org/min-53208.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Prachařite
Reference List:
Hålenius, Ulf, Hatert, Frédéric, Pasero, Marco, Mills, Stuart J. (2018) IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) NEWSLETTER 46. European Journal of Mineralogy, 30 (6) 1181-1189 doi:10.1127/ejm/2018/0030-2819
Localities for Prachařite
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.
Greece (TL) | |
| Hålenius et al. (2018) +2 other references |
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