400 Artificial Felspar Crystals, 



ADDITIONAL NOTICES. 



Account of Artificial Felspar, by Professor Kersten. — Pro- 

 fessor Kersten, as appears from a Number of Poggendorrs 

 Annalen, No. 22. for 1834, has found distinctly formed crystals 

 of prismatic felspar on the walls of a furnace, in which copper 

 slate and copper ores were melted. Among these pyro-chemi- 

 cally formed crystals, some were simple, others twin. The sur- 

 face of the crystals was smooth or vertically streaked ; fracture 

 conchoidal. Lustre of the crystals vitreous, and colour rose red, 

 passing into violet blue. Are opaque, brittle, and hardness = 6 

 of Mohs' scale. Chemical trials proved that they are composed 

 of silica, alumina, and potash, consequently the same consti- 

 tuents as felspar. As accidental parts, traces of manganese and 

 lime may be mentioned. Mitscherlich, who examined these ar- 

 tificial felspar crystals, says, they exhibited the primitive planes 

 of the oblique prism, and were truncated on ^he acuter lateral 

 edges ; a distinct cleavage was observed parallel with the trun- 

 cating and terminal planes, which meet under an angle of 90°. 

 Hitherto every attempt to make felspar crystals by artificial 

 means has failed ; hence, in a geological point of view, this fact 

 of Kersten's is of very great importance. 



Crystals of Oxide of Chrome. — Professor Wohler has pre- 

 pared beautiful crystals of this mineral. These crystals were 

 both single and twin, belonging to the same rhomboidal series as 

 corundum. One of the most interesting features in these crystals 

 is their great hardness, it being equal to that of corundum. 



Phosphate of Lime in the Teeth, and Silica in the Skin, of 

 the Infisoria.'—Rose of Berlin has ascertained, that the hard 

 parts which in certain tribes of infusory animals are called teeth, 

 are composed of phosphate of lime ; and that the hard case or 

 cover with which many of these minute creatures are protected, 

 is composed of silica. 



