[ *33 3 



h. Siliceous Schistus with Mullen ; colour blu- 

 ifh grev, it's furface often ftained reddifh or yel- 

 lowifh brown ; fracture fine, fplintery, and uneven. 



i. Pitchstone ivith Opal ; of a pearl grey, refem- 

 bling porcelanite ; penetrated with lumps of opal ; 

 brittle; imbibes water (lowly ; decrepitates ftrongly 

 by heat, and then whitens, and remains in a loofc 

 powder, 



III. Aggregated. 



A. CALCAREOUS. 



a. Calcareous Sandstone ; cryftallized in rhom- 

 boids ; amorphous ; colour generally white or 

 grey, or yellowifh white ; furface rough ; fra&ure 

 earthy or flaty ; often fpangled with mica. Anal. 

 Carbonate of lime 37,5. Silex 62,5. Lassone. 



b. Calcareous Breccia ; confiding of fragments 

 of marble in a calcareous cement. 



B. MAGNESIAN. 



a. Potstone Porphyry ; amorphous, undulatingly 

 foliated; greenifh, reddifh, or yellowifh grey; 

 or fpeckled earth ; red or leek green; containing 

 potftone and feltfpar. 



b. Serpentine Porphyry ; amorphous, compacl ; 

 dark or olive green, grey, or reddifh ; fraclure 

 fplintery; found near Florence, containing fer- 

 pentine and feltfpar. 



C. ARGIL- 



