Lucchesiite
Lucchesiite is a new member of tourmaline-group of minerals.[3] Lucchesiite has the formula CaFe3Al6(Si6O18)(BO3)3(OH)3O. It is the calcium and oxygen-analogue of schorl.[3] It has two co-type localizations, one in Czech Republic and the other in Sri Lanka. As the other members of the tourmaline group, it is trigonal.[2][1]
| Lucchesiite | |
|---|---|
 | |
| General | |
| Category | Cyclosilicates Tourmaline group |
| Formula (repeating unit) | CaFe3Al6(Si6O18)(BO3)3(OH)3O |
| Crystal system | Trigonal |
| Crystal class | Ditrigonal pyramidal (3m) (same H-M symbol) |
| Space group | R3m |
| Unit cell | a = 16.00, c = 7.21 [Å] (approximated); Z = 3 |
| Identification | |
| Color | Black |
| Crystal habit | Thin tablets |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 7 |
| Luster | Vitreous |
| Streak | Grey |
| Density | 3.21 (calc.), 3.24 (meas.) (approximated) |
| Optical properties | Uniaxial (-) |
| Pleochroism | Very dark brown to light brown |
| References | [1][2][3] |
Notes on chemistry
Impurites in lucchesiite, depending on the provenience, are sodium, magnesium, aluminium, titanium, trivalent iron, and minor vanadium, potassium, manganese and zinc.[1]
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References
- Bosi, F., Skogby, H., Ciriotti, M.E., Gadas, P., Novák, M., Cempírek, J., Všianský, D., and Filip, J., 2016. Lucchesiite, CaFe2+3Al6(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup. Mineralogical Magazine 80(1)
- Bosi, F., Skogby, H., Ciriotti, M.E., Gadas, P., Novák, M., Cempírek, J., Všianský, D., and Filip, J., 2015. Lucchesiite, IMA2015-043. CNMNC Newsletter No. 27, October 2015, page ; Mineralogical Magazine 79, 1229–1236
- "Lucchesiite: Lucchesiite mineral information and data". Mindat.org. Retrieved 2016-03-04.
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