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Theisite
A valid IMA mineral species
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About Theisite
Nicholas J. Theis
Formula:
Cu5Zn5(AsO4,SbO4)2(OH)14
Colour:
Greenish blue, turquoise-blue, pale turquoise-green, pale emerald-green
Lustre:
Pearly
Hardness:
1½
Specific Gravity:
4.3
Crystal System:
Orthorhombic
Name:
Named in honour of Nicholas James Theis (29 July 1946, Willmar, Minnesota, USA - 5 July 2021, Carollton, Texas, USA), geologist, Bendix Corporation. Along with Michael E. Madson, he discovered the mineral.
Type Locality:
Rare secondary mineral in fahlore deposits.
The crystal structure is unknown. Unlike in the formula suggested in the original publication, the Sb is probably present in octahedral coordination as Sb(OH)6 or Sb(H2O)6 groups.
See also "genèvéite".
Chemically similar to sabelliite.
Visually similar to tyrolite.
The crystal structure is unknown. Unlike in the formula suggested in the original publication, the Sb is probably present in octahedral coordination as Sb(OH)6 or Sb(H2O)6 groups.
See also "genèvéite".
Chemically similar to sabelliite.
Visually similar to tyrolite.
Unique Identifiers
Mindat ID:
3934
Long-form identifier:
mindat:1:1:3934:1
IMA Classification of Theisite
Approved
IMA Formula:
Cu2+5Zn2+5As5+2O8(OH)14
Approval year:
1980
Classification of Theisite
8.BE.75
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
E : With only medium-sized cations, (OH, etc.):RO4 > 2:1
8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H2O
E : With only medium-sized cations, (OH, etc.):RO4 > 2:1
41.1.2.1
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
1 : (AB)m(XO4)pZq, where m:p > 4:1
41 : ANHYDROUS PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
1 : (AB)m(XO4)pZq, where m:p > 4:1
24.2.5
24 : Antimonates and Antimonites
2 : Antimonates of Be, Mg, Ca, Zn or Hg
24 : Antimonates and Antimonites
2 : Antimonates of Be, Mg, Ca, Zn or 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 |
|---|---|---|
| Ths | 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 Theisite
Pearly
Transparency:
Translucent
Comment:
Pearly on cleavages
Colour:
Greenish blue, turquoise-blue, pale turquoise-green, pale emerald-green
Streak:
Off-white
Hardness:
1½ on Mohs scale
Tenacity:
Sectile
Cleavage:
Perfect
{001}
{001}
Density:
4.3 g/cm3 (Measured) 4.45 g/cm3 (Calculated)
Optical Data of Theisite
Type:
Biaxial (-)
RI values:
nα = 1.755 nβ = 1.785 nγ = 1.785
Max. Birefringence:
δ = 0.030
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:
Very High (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.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
distinct to strong
Comments:
nearly uniaxial (–)
Chemistry of Theisite
Mindat Formula:
Cu5Zn5(AsO4,SbO4)2(OH)14
Element Weights:
Crystallography of Theisite
Crystal System:
Orthorhombic
Cell Parameters:
a = 8.222(2) Å, b = 7.123 Å, c = 14.97(3) Å
Ratio:
a:b:c = 1.154 : 1 : 2.102
Unit Cell V:
876.72 ų (Calculated from Unit Cell)
Z:
2
Comment:
pseudohexagonal. Point group: n.d.; space group: n.d. (no possible space groups were suggested in the original description).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 14.97 Å | (9) |
| 7.483 Å | (5) |
| 4.112 Å | (4) |
| 3.741 Å | (10) |
| 2.534 Å | (9) |
| 1.830 Å | (5) |
| 1.533 Å | (5) |
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 Theisite
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1984,478.
Associated Minerals at Type Locality:
Synonyms of Theisite
Other Language Names for Theisite
Common Associates
Associations Based on Photo Data:
| 150 photos of Theisite associated with Azurite | Cu3(CO3)2(OH)2 |
| 54 photos of Theisite associated with Claraite | (Cu,Zn)15(CO3)4(AsO4)2(SO4)(OH)14 · 7H2O |
| 21 photos of Theisite associated with |
Black Pine Mine, Philipsburg Mining District, Granite County, Montana, USA