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Woodwardite
A valid IMA mineral species - grandfathered
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About Woodwardite
Samuel Pickworth Woodward
Formula:
Cu1-xAlx(OH)2(SO4)x/2 · nH2O
where (x < 0.5, n < 3x/2); Cu:Al ratios stated to fall between 1.73 and 2.03.
Colour:
Greenish-blue, turquoise-blue
Lustre:
Waxy, Dull
Hardness:
2
Specific Gravity:
2.38
Crystal System:
Trigonal
Member of:
Name:
Named after Samuel Pickworth Woodward (17 September 1821 – 11 July 1865), English naturalist and geologist. In 1845, S. P. Woodward became the professor of geology and natural history in the Royal Agricultural College, Cirencester. In 1848, he was appointed assistant in the department of geology and mineralogy in the British Museum. He proposed the term Bernician Series for the lower portion of the Carboniferous System, below the Millstone Grit.
Type Locality:
Unique Identifiers
Mindat ID:
4314
Long-form identifier:
mindat:1:1:4314:0
IMA Classification of Woodwardite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
(Cu2+,Al)9(S6+O4)2(OH)18·nH2O
First published:
1866
Classification of Woodwardite
7.DD.35
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
31.2.2.1
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
2 : (AB)6(XO4)Zq·xH2O
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
2 : (AB)6(XO4)Zq·xH2O
25.2.21
25 : Sulphates
2 : Sulphates of Cu and Ag
25 : Sulphates
2 : Sulphates of Cu and Ag
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 |
|---|---|---|
| Wwd | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Woodwardite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Woodwardite
Waxy, Dull
Transparency:
Translucent, Opaque
Colour:
Greenish-blue, turquoise-blue
Streak:
Pale blue
Hardness:
2 on Mohs scale
Density:
2.38 g/cm3 (Measured)
Optical Data of Woodwardite
Type:
Biaxial (+)
RI values:
nα = 1.552 - 1.571 nβ = 1.555 - 1.574 nγ = 1.565 - 1.576
Max. Birefringence:
δ = 0.005 - 0.013
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:
Low (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 (71°) 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 (71°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
strong
Chemistry of Woodwardite
Mindat Formula:
Cu1-xAlx(OH)2(SO4)x/2 · nH2O
where (x < 0.5, n < 3x/2); Cu:Al ratios stated to fall between 1.73 and 2.03.
where (x < 0.5, n < 3x/2); Cu:Al ratios stated to fall between 1.73 and 2.03.
Crystallography of Woodwardite
Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R3m
Cell Parameters:
a = 5.306(2) Å, c = 26.77(2) Å
Ratio:
a:c = 1 : 5.045
Unit Cell V:
652.70 ų (Calculated from Unit Cell)
Morphology:
Occurs as minute, botryoidal concretions with a fine-fibrous structure; spherulitic.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.9 Å | (100) |
| 4.47 Å | (90) |
| 2.65 Å | (30) |
| 2.55 Å | (60) |
| 2.28 Å | (50) |
| 1.98 Å | (30) |
| 1.53 Å | (30) |
Comments:
See also ICDD 39-0726.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-𝑇 alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits | |
| Stage 5: Initiation of plate tectonics | <3.5-2.5 |
| 42 : Sea-floor Mn nodules | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47b : [Sulfates and sulfites] |
Geological Setting:
secondary mineral in the oxidized zone of copper deposits
Type Occurrence of Woodwardite
General Appearance of Type Material:
Stalactitic forms consisting of minute botryoidal aggregations. Crusts a couple millimeters in thickness, possessing the peculiar rippled appearance. Without traces of crystalline structure.
Other Language Names for Woodwardite
Relationship of Woodwardite to other Species
Member of:
Other Members of Woodwardite Group:
| Honessite | (Ni1-xFe3+x)(OH)2[SO4]x/2 · nH2O | Trig. |
| Zincowoodwardite | Zn1-xAlx(OH)2[SO4]x/2 · nH2O | Trig. |
Maid of Sunshine Mine, Courtland, Turquoise Mining District, Cochise County, Arizona, USA