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Ktenasite
A valid IMA mineral species - grandfathered
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About Ktenasite
Konstantinos Ktenas
Formula:
ZnCu4(SO4)2(OH)6 · 6H2O
Originally given as (Cu,Zn)5(SO4)2(OH)6.6H2O; changed to present formula by executive decision taken by the CNMNC during approval of fehrite.
Colour:
Blue-green to emerald-green
Lustre:
Vitreous
Hardness:
2 - 2½
Specific Gravity:
2.94 - 2.97
Crystal System:
Monoclinic
Member of:
Name:
Named by P. Kokkoros in 1950 after Konstantinos A. Ktenas (1885-1935), Greek physician, professor of mineralogy and petrology (since 1908). Dean (1918) of the National and Kapodistrian University of Athens, Director of the Museum of Mineralogy and Palaeontology and of the Zoological Museum of the University (1918). Head of the Greek Geological Survey and one of the founding members of the Academy of Athens (1926).
Rare secondary copper-zinc sulphate with typical pseudo-orthorhombic habit.
The Zn analogue of gobelinite and fehrite.
Mg- or Cd-bearing varieties are also known (U. Kolitsch & G. Giester, unpublished results), as well as a Zn-dominant (on one of the Cu sites) analogue (Unnamed (Zn-analogue of Ktenasite)) and a Ni-dominant analogue, asagiite.
Ktenasite may have to be split up into a Cu- and a Zn-dominant species; the crystal structure contains a Zn site, a Cu site and a mixed Cu/Zn site with variable occupancy (U. Kolitsch & G. Giester, unpublished results). Data of Livingstone (1991) suggest dominant Zn on at least two sites, although this suggestion is based only on chemical analyses.
A joint proposal on the complex nomenclature of ktenasite-type minerals is in preparation (Leverett, Sciberras, Williams, Kolitsch, Giester, Hibbs et al., 2009-2020).
The Zn analogue of gobelinite and fehrite.
Mg- or Cd-bearing varieties are also known (U. Kolitsch & G. Giester, unpublished results), as well as a Zn-dominant (on one of the Cu sites) analogue (Unnamed (Zn-analogue of Ktenasite)) and a Ni-dominant analogue, asagiite.
Ktenasite may have to be split up into a Cu- and a Zn-dominant species; the crystal structure contains a Zn site, a Cu site and a mixed Cu/Zn site with variable occupancy (U. Kolitsch & G. Giester, unpublished results). Data of Livingstone (1991) suggest dominant Zn on at least two sites, although this suggestion is based only on chemical analyses.
A joint proposal on the complex nomenclature of ktenasite-type minerals is in preparation (Leverett, Sciberras, Williams, Kolitsch, Giester, Hibbs et al., 2009-2020).
Unique Identifiers
Mindat ID:
2282
Long-form identifier:
mindat:1:1:2282:4
IMA Classification of Ktenasite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Zn2+Cu2+4(S6+O4)2(OH)6·6H2O
Classification of Ktenasite
7.DD.20
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
D : With only medium-sized cations; sheets of edge-sharing octahedra
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
D : With only medium-sized cations; sheets of edge-sharing octahedra
31.6.3.1
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
6 : (AB)5(XO4)2Zq·xH2O
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
6 : (AB)5(XO4)2Zq·xH2O
25.5.4
25 : Sulphates
5 : Sulphates of Zn and Hg
25 : Sulphates
5 : Sulphates of Zn and Hg
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 |
|---|---|---|
| Kte | 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 Ktenasite
Vitreous
Transparency:
Transparent
Colour:
Blue-green to emerald-green
Hardness:
2 - 2½ on Mohs scale
Density:
2.94 - 2.97 g/cm3 (Measured) 2.97 g/cm3 (Calculated)
Optical Data of Ktenasite
Type:
Biaxial (-)
RI values:
nα = 1.574 nβ = 1.613 - 1.615 nγ = 1.623 - 1.628
2V:
Measured: 51° to 59°, Calculated: 50°
Max. Birefringence:
δ = 0.049 - 0.054
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 (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
r > v
Pleochroism:
Visible
Comments:
X = colorless; Y = bluish green; Z = pale green.
Chemistry of Ktenasite
Mindat Formula:
ZnCu4(SO4)2(OH)6 · 6H2O
Originally given as (Cu,Zn)5(SO4)2(OH)6.6H2O; changed to present formula by executive decision taken by the CNMNC during approval of fehrite.
Originally given as (Cu,Zn)5(SO4)2(OH)6.6H2O; changed to present formula by executive decision taken by the CNMNC during approval of fehrite.
Element Weights:
Chemical Analysis
wt%
| 1 | |
|---|---|
| Cu | 37.9 % |
| Zn | 16.6 % |
| S | 24.0 % |
| H | 22.0 % |
| Total: | 100.5 % |
Crystallography of Ktenasite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Setting:
P21/c
Cell Parameters:
a = 5.596(2) Å, b = 6.122(1) Å, c = 23.766(5) Å
β = 95.55°
β = 95.55°
Ratio:
a:b:c = 0.914 : 1 : 3.882
Unit Cell V:
810.38 ų (Calculated from Unit Cell)
Z:
2
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0010799 | Ktenasite | Mellini M, Merlino S (1978) Ktenasite, another mineral with 2[(Cu,Zn)2(OH)3O]- octahedral sheets Zeitschrift fur Kristallographie 147 129-140 |  | 1978 | Miniera Trentin, Vicenza, Italy | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 11.9 Å | (10b) |
| 2.74 Å | (10) |
| 5.87 Å | (9) |
| 4.85 Å | (9) |
| 3.53 Å | (9) |
| 1.704 Å | (9) |
| 2.95 Å | (6) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 55 : Anthropogenic mine minerals | |
| 56 : Slag and smelter minerals (see also #51 and #55) |
Type Occurrence of Ktenasite
General Appearance of Type Material:
Tabular crystals, to 1 mm
Place of Conservation of Type Material:
University of Thessalonika, Thessalonika, Greece
Geological Setting of Type Material:
formed by oxidation of chalcopyrite and sphalerite
Associated Minerals at Type Locality:
Other Language Names for Ktenasite
Dutch:
Veneziana gallery, Monte Trisa Mines, Mercanti Valley, Torrebelvicino, Vicenza Province, Veneto, Italy