Lucchesiite

Lucchesiite
General
Category Cyclosilicates
Tourmaline group
Formula
(repeating unit)
CaFe3Al6(Si6O18)(BO3)3(OH)3O
Crystal system Trigonal
Crystal class Ditrigonal pyramidal (3m)
H-M symbol: (3m)
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]

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]

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]

References

  1. 1 2 3 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)
  2. 1 2 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
  3. 1 2 3 "Lucchesiite: Lucchesiite mineral information and data". Mindat.org. Retrieved 2016-03-04.
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