May 14 2014
Ribbeite is an orthorhombic-dipyramidal pink mineral. It contains silicon, oxygen, manganese, magnesium, and hydrogen, and is a member of the humite group.
The mineral was first discovered in 1987 in the Kombat mine, Namibia. It was named after Paul Ribbe of Virginia Polytechnical Institute and State University.
Properties of Ribbeite
The following are the key properties of Ribbeite:
- Cell Data
- Space Group: Pbnm or Pbn21
- a = 4.799(1)
- b = 10.742(6)
- c = 15.70(1)
- Z = 4
- Crystal Data
- Orthorhombic
- Point Group: 2/m 2/m 2/m or mm2
- Crystals: up to 0.5mm, in granular aggregates, to20 cm
- X-ray Powder Pattern: 1.796 (100), 2.873 (80), 2.552 (80), 2.925 (70), 2.821 (70), 2.695 (60), 2.515 (40)
- Chemical Composition
| Elements |
Content |
| MnO |
65.1 |
| SiO2 |
24.3 |
| MgO |
5.2 |
| H2O |
4.9 |
| FeO |
0.3 |
| CaO |
0.2 |
| Total |
100 |
- Optical Properties
- Optical Class: Biaxial (+)
- Pleochroism: Weak; X = Y = colorless; Z = light pink
- Orientation:X = b; Y = a; Z = c
- Dispersion: r > v; moderate
- Absorption: Z > X = Y
- α = 1.780(3)
- β = 1.792(3)
- γ = 1.808(3)
- 2V(meas.) = 81.3(2)°
- 2V(calc.) = 82.5°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 3.75 g/cm3
note: Specific gravity of Ribbeite = 3.90 g/cm3 |
| Photoelectric |
PERibbeite = 12.27 barns/electron
U = PERibbeite x ρElectron density = 46.06 barns/cm3 |
| Fermion index |
Fermion index = 0.01
Boson index = 0.99 |
Radioactivity
|
Ribbeite is not radioactive
|
How to Identify Ribbeite
Ribbeite is a transparent pink mineral, having vitreous luster and light pink streak. The density of ribbeite is 3.9g/cm3, and its hardness is 5.
Global Distribution
Ribbeite is widely distributed in the Kombat mine, 49km south of Tsumeb, Namibia.
Occurrence of Ribbeite and Useful Mineral Association
Ribbeite occurs in tectonically transported and boudinaged manganese-rich lenses within dolostones and mineralogically distinct layers.
It is closely associated with jacobsite, galaxite, chlorite, pyrochroite, manganoan calcite, and alleghanyite.
References