Dr J. Rienhard Blum on Pseudomorphous Minerals. 245 



dolite or reddish mica. The micarelle or micanite of Neu- 

 stadt is shewn by Dr Blum to be altered tourmaline, some 

 of the crystals having distinctly the form of that mineral. 



Prehnite with the form of Analcime. — These pseudomorphs 

 occur at Dumbarton, at Molignon in the Tyrol, and near 

 Wolfstein in the district of the Lower Rhine. At the last 

 locality they are associated with calc-spar and datholite in 

 diorite. The datholite appears to have been partially acted 

 upon at the time of the change, and is supposed to have 

 given the lime to the forming prehnite. 



Talc with the form of Kyanite. — These pseudomorphs have 

 been observed at Wustuben, in the Fichtelgebirge. The edges 

 of the crystals are rounded, and the surface is covered with 

 a thin crust of talc ; within they are a fine-grained aggregate 

 of talc, possessing the softness and other characters of this 

 mineral. The change consists in the substitution of magne- 

 sia for alumina. 



Talc with the form of Felspar. — This pseudomorph has 

 been found at the tin-mines of Altenberg in Saxony, associ- 

 ated with quartz, specular iron, and light-coloured talc. The 

 felspar crystals consist of talc in fine foliated grains ; they 

 have a rough drusy surface, yet tolerably sharp edges. 



Steatite with the form of Hornblende. — The Pargasite oc- 

 curring in granular limestone at Pargas, Finland, is some- 

 times altered to steatite of a greenish colour. From the 

 nature of the crystals, Dr Blum infers that the change com- 

 menced at the centre where it is most complete. It requires 

 the removal only of the lime. 



Steatite with the form of Quartz. — These pseudomorphs 

 occur at Gopfersgrun. The form and strice of the planes are 

 well preserved. Where the change is partial, the quartz has 

 become white, and without lustre ; when complete, all the 

 characteristics of the quartz are lost except the external form, 

 and a soft earthy steatite has taken its place. 



Dr Marx has suggested, that the magnesia that caused the 

 change came from the bitter spar ; but Dr Blum urges, in 

 opposition to this view, that the magnesia in this mineral is in 

 Bmall quantities, and still remains in the bitter spar pseudo- 



