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
CategoryCyclosilicates
Tourmaline group
Formula
(repeating unit)
CaFe3Al6(Si6O18)(BO3)3(OH)3O
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
(same H-M symbol)
Space groupR3m
Unit cella = 16.00, c = 7.21 [Å] (approximated); Z = 3
Identification
ColorBlack
Crystal habitThin tablets
FractureConchoidal
TenacityBrittle
Mohs scale hardness7
LusterVitreous
StreakGrey
Density3.21 (calc.), 3.24 (meas.) (approximated)
Optical propertiesUniaxial (-)
PleochroismVery 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]

References

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