Rhodesite
A valid IMA mineral species - grandfathered
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About Rhodesite
Cecil Rhodes
Formula:
KHCa2Si8O19 · 5H2O
Colour:
White
Lustre:
Silky
Hardness:
3 - 4
Specific Gravity:
2.27 - 2.36
Crystal System:
Orthorhombic
Member of:
Name:
Named after Cecil John Rhodes (1853-1902), British colonial statesman and financier of the Rhodes University, South Africa. He ran the British South Africa Company, which operated in a territory that became known as Rhodesia (named after him, now the countries of Zimbabwe and Zambia). He also founded the De Beers diamond company.
Unique Identifiers
Mindat ID:
3403
Long-form identifier:
mindat:1:1:3403:2
Similar Names
| Magnesio-riebeckite | A valid IMA mineral species - grandfathered | ◻Na2(Mg3Fe23+)(Si8O22)(OH)2 |
| Rhodizite | A valid IMA mineral species - grandfathered | KBe4Al4(B11Be)O28 |
IMA Classification of Rhodesite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
K2Ca2Si8O19·5H2O
Classification of Rhodesite
9.EB.05
9 : SILICATES (Germanates)
E : Phyllosilicates
B : Double nets with 4- and 6-membered rings
9 : SILICATES (Germanates)
E : Phyllosilicates
B : Double nets with 4- and 6-membered rings
72.5.1.1
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
14.6.7
14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both
14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both
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 |
|---|---|---|
| Rod | 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 Rhodesite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Rhodesite
Silky
Transparency:
Transparent, Translucent
Colour:
White
Hardness:
3 - 4 on Mohs scale
Cleavage:
Distinct/Good
Good on {100}
Good on {100}
Density:
2.27 - 2.36 g/cm3 (Measured) 2.26 g/cm3 (Calculated)
Optical Data of Rhodesite
Type:
Biaxial (+)
RI values:
nα = 1.501 - 1.504 nβ = 1.506 - 1.508 nγ = 1.513 - 1.518
2V:
Calculated: 68.1°
Max. Birefringence:
δ = 0.012 - 0.014
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 (negative)
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:
relatively strong
Chemistry of Rhodesite
Mindat Formula:
KHCa2Si8O19 · 5H2O
Element Weights:
Common Impurities:
Al,Fe,Mg,Na
Crystallography of Rhodesite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Cell Parameters:
a = 23.60(18) Å, b = 6.57(2) Å, c = 7.03(2) Å
Ratio:
a:b:c = 3.592 : 1 : 1.07
Unit Cell V:
1,090.02 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Matted silky fibers, flattened rosettes, irregular segregations, crusts.
Comment:
Space Group: Pmam:
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0011015 | Rhodesite | Hesse K F, Liebau F, Merlino S (1992) Crystal structure of rhodesite, HK1-xNax+2yCa2-y(lB,3,22)(Si8O19)*(6-z)H2O, from three localities and its relation to other silicates with dreier double layers Zeitschrift fur Kristallographie 199 25-48 |  | 1992 | San Venanzo, Italy | 0 | 293 |
| 0011014 | Rhodesite | Hesse K F, Liebau F, Merlino S (1992) Crystal structure of rhodesite, HK1-xNax+2yCa2-y(lB,3,22)(Si8O19)*(6-z)H2O, from three localities and its relation to other silicates with dreier double layers Zeitschrift fur Kristallographie 199 25-48 | | 1992 | Trinity County, California, USA | 0 | 293 |
| 0011013 | Rhodesite | Hesse K F, Liebau F, Merlino S (1992) Crystal structure of rhodesite, HK1-xNax+2yCa2-y{lB,3,2}[Si8O19]*(6-z)H2O, from three localities and its relation to other silicates with dreier double layers Zeitschrift fur Kristallographie 199 25-48 | | 1992 | Zeilberg, Germany | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.548 Å | (100) |
| 4.386 Å | (47) |
| 5.901 Å | (34) |
| 6.302 Å | (32) |
| 5.032 Å | (28) |
| 2.864 Å | (25) |
| 2.762 Å | (23) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 7 : Ultramafic igneous rocks | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Geological Setting:
Kimberlite, altered silicic lavas
Type Occurrence of Rhodesite
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1957,18; National Museum of Natural History, Washington, D.C., USA, 114793.
Geological Setting of Type Material:
kimberlite pipe
Associated Minerals at Type Locality:
Other Language Names for Rhodesite
Relationship of Rhodesite to other Species
Member of:
Other Members of Rhodesite Group:
| Delhayelite | (Na,K)10Ca5Al6Si32O80(Cl2,F2,SO4)3 · 18H2O | Orth. |
| Fivegite | K4Ca2[AlSi7O17(O2-xOHx)][(H2O)2-xOHx]Cl | Orth. mm2 : Pmn21 |
| Hydrodelhayelite | KCa2AlSi7O17(OH)2 · 6H2O | Orth. mm2 |
| Melansonite | Na◻KZrSi8O19 · 5H2O | Orth. mmm(2/m2/m2/m) : Pmma |
| Monteregianite-(Y) | (Na,K)6(Y,Ca)2Si16O38 · 10H2O | Mon. 2/m |
| Natromelansonite | Na3Zr[Si7AlO19] · 4H2O | Mon. 2/m : P21/m |
Common Associates
Associations Based on Photo Data:
| 1 photo of Rhodesite associated with Tridymite | SiO2 |
| 1 photo of Rhodesite associated with Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O |
Related Minerals - Strunz-mindat Grouping
| 9.EB. | Natromelansonite | Na3Zr[Si7AlO19] · 4H2O |
| 9.EB.05 | Melansonite | Na◻KZrSi8O19 · 5H2O |
| 9.EB.05 | Macdonaldite | BaCa4Si16O36(OH)2 · 10H2O |
| 9.EB.10 | Hydrodelhayelite | KCa2AlSi7O17(OH)2 · 6H2O |
| 9.EB.10 | Delhayelite | (Na,K)10Ca5Al6Si32O80(Cl2,F2,SO4)3 · 18H2O |
| 9.EB.15 | Monteregianite-(Y) | (Na,K)6(Y,Ca)2Si16O38 · 10H2O |
| 9.EB.20 | Carletonite | KNa4Ca4Si8O18(CO3)4(OH,F) · H2O |
| 9.EB.20 | Fluorcarletonite | KNa4Ca4Si8O18(CO3)4F · H2O |
| 9.EB.25 | Günterblassite | (K,Ca,Ba)2(Fe,Ca,Mg,Na)[(Si,Al)13O25(OH)4] · 7H2O · |
| 9.EB.25 | Hillesheimite | (K,Ca,Ba,◻)2(Mg,Fe,Ca,◻)2[(Si,Al )13O23(OH)6](OH) · 8H2O |
| 9.EB.25 | Umbrianite | K7Na2Ca2[Al3Si10O29]F2Cl2 |
| 9.EB.30 | Fivegite | K4Ca2[AlSi7O17(O2-xOHx)][(H2O)2-xOHx]Cl |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 5.2906% | 1,640 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
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 Rhodesite
mindat.org URL:
https://www.mindat.org/min-3403.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Rhodesite
Reference List:
Mountain, E. D. (1957) Rhodesite, a new mineral from the Bultfontein mine, Kimberley. Mineralogical Magazine and Journal of the Mineralogical Society, 31 (239). 607-610 doi:10.1180/minmag.1957.31.239.01
Gard, J. A., Taylor, H. F. W., Chalmers, R. A. (1957) An investigation of two new minerals: rhodesite and mountainite. Mineralogical Magazine and Journal of the Mineralogical Society, 31 (239). 611-623 doi:10.1180/minmag.1957.31.239.02
Mountain, E. D. (1957) Rhodesite, a new mineral from the Bultfontein mine, Kimberley. Mineralogical Magazine and Journal of the Mineralogical Society, 31 (239). 607-610 doi:10.1180/minmag.1957.31.239.01
Sheppard, Richard A., Gude 3rd, Arthur J. (1969) Rhodesite from Trinity County, California. American Mineralogist, 54 (1-2). 251-255
Localities for Rhodesite
Showing 13 localities.
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.
Austria | |
| Exel (1993) +1 other reference |
| Postl (1987) +2 other references |
| Taucher (1989) |
Germany | |
| Jakob (1976) +2 other references |
| Personal information of Erich Keck +1 other reference |
| |
| Blaß et al. (1996) |
Italy | |
| Stoppa et al. (1997) +1 other reference |
South Africa (TL) | |
| Mountain (1957) +1 other reference |
Tanzania | |
| Tony Peterson Collection +1 other reference |
Ukraine | |
| Baranov et al. (2009) | |
USA | |
| Färber (n.d.) |
| Sheppard et al. (1969) +3 other references |
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Stradner Kogel, Wilhelmsdorf, Bad Gleichenberg, Südoststeiermark District, Styria, Austria