of Mixed Rocks. xi 



Principal varieties. 



Glandulous P The crystals more or )ess well formed, rather 



equally disseminated, and enveloped in a 

 phyllade, which is commonly micaceous. 

 Porphyritic. With crystals of felspar, &c. 

 (Environs of Anger. Deville and Laifour, 

 department of the Ardennes, Omalius d' 

 If alloy.) 

 Quartzose. With grains of quartz. 

 (Banks of the Mayenne near Angers.) 

 Chiastoliteferous. With crystals of chias- 



tolite. 

 (Alen^on. Tourmalet, Comelie, &c. in the 

 Pyrenees. Burkhartswald in Saxony.) 



Micaceous P Mica more or less abundantly disseminated 



in a phyllade, without any other accessory 

 mineral, neither staining, nor whitening 

 by the fire. 

 Platy. The mica disseminated in distinct and 



abundant plates. 

 Cnie greater part of grey wacke slates. Pla- 

 nitz in Saxony. Combe de Gilliarde in 

 Oisans.) 

 Satiny. Mica in scarcely distinct plates, the 



lustre silky. 

 (Schneeberg. Tourmalet in the Pyrenees.) 

 Dull. The mica disseminated in rare plates, 



aspect dull. 

 (Viel-Salm, department of the Ourte &c.) 



Carbc RATED P Slightly micaceous, stains black, and is 



sometimes calcariferous. 

 (Bagnere de Luchon. Hermersdorf in Saxony. 

 Hofnungstolle, in tha Hartz. Some marly 

 bituminous schists of Thuringia.) 



Species 2. CALSCHISTE. 



Argillaceous slate, often predominant, and limestone dis- 

 seminated either in elongated patches, small veins, or thin 

 plates, sometimes parallel, sometimes traxersing. The struc- 

 ture slaty. 



Obs. This mixture of limestone and argillaceous slate is 

 too constant in its structure, proportions, and character to 

 be regarded as accidental, or as an argillaceous slate traversed 



