http://www.mindat.org/min-3578.htmlSchorl
Formula: [Na][Fe2+3][Al6][(OH)3|OH|(BO3)3|Si6O18]
System: TrigonalColour:Bluish-black to black, ...
Lustre: Vitreous, ResinousHardness:7
Name:The early history of the mineral schorl shows that the name "Schorl" was in use prior to the year 1400 (AD) because a village known today as Zschorlau (in Saxony, Germany) was then named "Schorl" (or minor variants of this name). This village had a nearby tin mine where, in addition to cassiterite, a lot of black tourmaline was found.
http://oxforddictionaries.com/view/entry/m_en...schorl
a black iron-rich variety of tourmaline
http://de.wikipedia.org/wiki/Turmalingruppe.....
Schörl
Am häufigsten kommt der Fe-Turmalin mit dem Namen Schörl vor. Die erste genauere Beschreibung von Schörl mit der Bezeichnung „schürl“ und dessen Vorkommen im Sächsischen Erzgebirge erfolgte 1562 durch Johannes Mathesius (1504–1565).
http://www.mineralienatlas.de/lexikon/index.p...Als Schörl wird der auf den ersten Blick "schwarze" Turmalin bezeichnet.
Chemische Formel NaFe32+Al6(BO3)3Si6O18(OH)4
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http://www.britannica.com/facts/5/240384/scho...Greisen is closely connected with schorl, both in its mineralogical composition and in its mode of origin. Schorl is a pneumatolytic product consisting of quartz, tourmaline, and, often, white mica and thus passes into greisen. Both of these rocks frequently contain small percentages of cassiterite (tin oxide)...
http://books.google.de/books?id=Ma_HRIBQJmIC...Basler Taufstein, Kreuzstein, Schörlstein schorl rock
http://books.google.de/books?id=oG8EAAAAYAAJ... 
