| Balliranoite | |
| Category: | Tectosilicates |
| Formula: | (Na,K)6Ca2(Si6Al6O24)Cl2(CO3) |
| Imasymbol: | Blr[1] |
| System: | Hexagonal |
| Class: | 6 - Pyramidal |
| Symmetry: | P63 |
| Unit Cell: | a = 12.696 Å, c = 5.327 Å, V = 743.6 Å3, Z = 1 |
| Color: | Colorless |
| Habit: | Prismatic |
| Cleavage: | Perfect on (10-10) |
| Fracture: | Irregular/Uneven |
| Tenacity: | Brittle |
| Mohs: | 5 |
| Luster: | Vitreous |
| Opticalprop: | uniaxial positive |
| Streak: | White |
| Density: | 2.48 g/cm3 |
| References: | [2] [3] [4] |
Balliranoite ((Na,K)6Ca2(Si6Al6O24)Cl2(CO)3) is a mineral that was discovered at Monte Somma – Vesuvio volcanic complex, Campania, Italy. This mineral is named in honor of Paolo Ballirano (b. 1964), Italian crystallographer and professor in the Department of Earth Sciences, University of Rome ‘‘La Sapienza’’, who has made important contributions to the crystal chemistry of cancrinite-group minerals.
Balliranoite is found in an alkaline skarnlike rock composed of orthoclase, phlogopite, clinohumite, calcite, diopside, pargasite, haüyne, apatite and balliranoite,[5] as product of the metasomatic interactions between alkaline magma and limestone. These chemical alterations by hydrothermal and other fluids replace elements in the chemical structure, changing the mineral composition of the rock.
The idealized formula for balliranoite is (Na,K)6Ca2(Si6Al6O24)Cl2(CO3), and the empirical formula based on 12 Si atoms with isomorphic substitution by Al atoms is: Na4.70Ca2.53K0.73(Si6.02Al5.98O23.995)Cl2.34(CO3)0.82(SO40.27*0.12H2O. This is a uniaxial (+) mineral with w = 1.523(2), e = 1.525(2), composed of the following compounds:
| Compound | wt% | Range | |
|---|---|---|---|
| Na2O | 13.05 | 12.80-13.24 | |
| K2O | 3.08 | 3.01-3.16 | |
| CaO | 12.70 | 12.56-12.85 | |
| Al2O3 | 27.28 | 27.17-27.42 | |
| SiO2 | 32.38 | 32.23-32.55 | |
| CO2 | 3.24 | 3.18-3.30 | |
| SO3 | 1.96 | 1.79-2.10 | |
| Cl | 7.43 | 7.20-7.70 | |
| H2O | 0.19 | 0.15-0.23 | |
| -O=Cl2 | -1.68 | - | |
| Total | 99.63 | - |
The powder diffraction data for balliranoite is:
| d-spacing (Å) | Intensity | |
|---|---|---|
| 4.797 | (100) | |
| 3.669 | (57) | |
| 3.281 | (73) | |
| 2.754 | (16) | |
| 2.662 | (58) | |
| 2.648 | (13) | |
| 2.446 | (31) | |
| 2.120 | (18) |