1818.] Scientific Intelligence. 311 



ties, and exhibiting superficially right prisms with square bases 

 terminated by truncated pyramids, the faces of which are placed 

 on the angles of the prism. The structure of the grains is gra- 

 nularly foliated with joints parallel to the bases. The colour 

 both of the grains and crystals is an opaque white. When 

 digested in hot nitric acid, it soon gelatinizes, and the same 

 effect takes place in cold acid after a few days. From these 

 characters it is manifest that this supposed new species is only 

 a variety of mesotype. 



Egeran. — This substance has been so named by Werner from 

 the place where it was discovered, Eger, in Bohemia. Its 

 gangue is a grey quartz covered in part with tremolite. It occurs 

 in the form of small, nearly opaque crystals, of a deep brown 

 colour. The form of the crystals is a right rectangular prism, 

 each longitudinal edge of which is replaced by a facette forming 

 an angle of 135° with the two adjacent sides. It possesses 

 natural joints parallel to the four principal sides and to the bases : 

 before the blow-pipe it melts into a black scoria. Hence it is 

 clear that this supposed new mineral is idocrase. 



Gehlenite. — So named by M. Fuchs in honour of the chemist 

 Gehlen. It was discovered in the valley of Fassa, and has the 

 form of small rectangular crystals, sometimes single, often imbri- 

 cated, disseminated in a gangue of lamellar calcareous spar. The 

 form of the crystals is a right prism with square bases, so low as 

 to be almost tabular. The colour is grey with a greenish or 

 yellowish tinge. The surface is dull, rough to the touch as if 

 corroded. The crystals are opaque, or nearly so, and somewhat 

 inferior in hardness to quartz. The fracture is uneven, passing 

 to splintery, with indications of joints parallel to the bases. 

 Specific gravity, 2-98. Before the blow-pipe it melts into a 

 brownish yellow transparent glass, which soon becomes opaque 

 and scoriform when acted on by the interior part of the flame. 



It is to be remarked that the crystals are often traversed by 

 minute veins of calcareous spar, and when reduced to impalpable 

 powder, the mineral dissolves in muriatic acid, and the solution 

 gelatinizes. The same property has been observed by M. Cor- 

 dier in the idocrase of Barreges, which occurs also in a calca- 

 reous base. Hence M. Cordier is induced to regard the 

 gehlenite as a variety of idocrase. 



llclvin. — This substance, so named by Werner, was discovered 

 in the mine of Schwartzenberg, in Saxony. It occurs in a black- 

 ish green chlorite mixed with blende and fluor, in the form of 

 minute disseminated irregular octohedrons, of a pale yellowish 

 brown colour. Its fracture offers no indication of natural joints. 

 It is softer than glass, and melts easily before the blow-pipe into 

 a blackish brown glass. The mineral acids when cold appear 

 to have no action on its powder. 



Petiuni — So named by Werner, was discovered at Bodemnais, 

 ia Bavaria. It occurs imbedded in grey granite, in crystalline 



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