MODE IV. WACKEN. 273 



formerly celebrated as absorbents, and which 

 are now supplanted by magnesia, are merely 

 fine clays, which contain a small portion of 

 magnesian earth. Hence they somewhat ap- 

 proach in their nature to the fullers' earth of 

 Berkshire, and Ryegate in Surry*. 



The earth called almagra, which is used to 

 impart a red colour, and an unctuous feel, to 

 Spanish snuff, is found at Almazaran, near Car- 

 thagena, in Spain, and seems a fine ferruginous 

 clay, perhaps with a mixture of magnesia. 



MODE IV. WACKEN. 



Texture, sometimes compact, sometimes vesi- Characters, 

 cular. When the vesicles are filled with para- 

 sitic stones, it is called amygdalite ; but as the 

 base of the latter is more frequently a trap or 

 basaltin, it has been classed after that substance. 



Hardness, marmoric, sometimes gypsic. Frac- 

 ture, commonly even, sometimes approaching 

 the flat conchoidal. Fragments, amorphous, 

 rather blunt. 



Weight, granitose. 



* Bergman has put Hampshire, in which he is followed by all 

 the foreign mineralogists ; but there is no fullers' earth in Hamp- 

 shire. 



VOL. I. T 



