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Download hereGENERAL DESCRIPTION
Schorl is a mineral that belongs to the group of tourmalines. Schorls are hydrated aluminoborosilicates of sodium and iron. It is formed in the granitic pegmatites, diorites and some gabbros, in the greisens, the skarns and quartz veins of varied origins, even in metamorphic context.
The prismatic and acicular crystals even flattened, they are transparent with almost opaque. Their colour is brown-blackish to black and have a vitreous luster.
Schorl, like all the species belonging to the group of tourmalines, is pyrolectric and piezoelectric.
Among the very many schorl localities, one will quote Conselheiro Pena in Brazil where the crystals are striated and can measure up to 10 cm; the pegmatite of Benedito Viola also in Brazil where the crystals reach 30 cm. A recent trip (2007) of the Muséum national d’Histoire naturelle Natural in the Arendal area of Norway brought back very fresh and brilliant crystals of 5-10 cms in length.
In France, schorl is present in many areas (Massif Central, Vosges, Pyrénées, Brittany etc) but often in the form of small acicular crystals.
The place of conservation of the type of this species (Schorl village, known currently under the name of Zschorlau; Saxony, Germany) is not definable as the species was recognized since, at least, the XVth century by the tin miners of this Saxon locality.
HISTORY : Species named after the German village Schorl which was located near mines where black tourmalin as found
Species first described in 1524 by Johannes Mathesius (1504-1565), German theologian
Type-locality: undefined because species already known from the Ancients
CHEMICAL FORMULA : Na Fe3 Al6 (BO3) Si6O18 (OH)4
CRYSTAL SYSTEM : Hexagonal
COLOR : Brown, black
DIAPHANIETY : Transparent to almost opaque
LUSTER : Vitreous to resineous
STREAK : White
MORPHOLOGIE : Prismatic to acicular crystals, radial, fibrous, massive
HARDNESS : 7
CHEMICAL CLASS: 3,244
DENSITY : VIII - Silicates
GROUP : Tourmaline
STRUNZ CLASS BEFORE 2001 : 8/E.19-50
STRUNZ CLASS AFTER 2001 : 8.CK.05
