Outlines of mineralogy / by J. Kidd.

  • Kidd, John, 1775-1851.
Date:
1809
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of mineralogy / by J. Kidd. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    Tourmaline. Short, of Kirwan; as applied to those varieties which are black. The term shorl, or schorl, as it is sometimes written, is derived from the name of the village of Schorlaw in Saxony; where the substance first called shorl was found. It has been customary till lately to apply this term to a great variety of crystallized substances; parti- cularly those of a prismatic form. Tourmaline, of Kirwan ; as applied to those varieties w hich are of a green colour. Black shorl, and Electric shorl; of many mineralo- gists. Cockle, of the Cornish miners; as applied to the va- rieties which are black. In hardness it is inferior to quartz; but scratches glass. According to Hally it is fusible by the blow-pipe into a white or grey enamel, whatever the original colour may have been. Electric, by heat; positively at one extremity, nega- tively at the other : when the electricity is excited by friction it is always positive. The transparent varieties are most electric. Specific gravity varies from 3,08 to 3,35. Primitive form, an obtuse rhomboid; the plane angles of which are 113' 35' and 66' 2o', according to Haliy; according to Count Bournon 114'' 12' and GS 48', VOL. I. 2 il