Lucchesiite | |
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General | |
Category |
Cyclosilicates Tourmaline group |
Formula (repeating unit) | CaFe3Al6(Si6O18)(BO3)3(OH)3O |
IMA symbol | Lcc [1] |
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 | [2] [3] [4] |
Lucchesiite is a new member of tourmaline-group of minerals. [4] Lucchesiite has the formula CaFe3Al6(Si6O18)(BO3)3(OH)3O. It is the calcium and oxygen-analogue of schorl. [4] 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. [3] [2]
Impurites in lucchesiite, depending on the provenience, are sodium, magnesium, aluminium, titanium, trivalent iron, and minor vanadium, potassium, manganese and zinc. [2]