MODE VII. ARGILLACEOUS INTRITE. 81 



or the stony mountain, is twenty stages from the 

 same city. This marble is so hard, that they 

 must soften it with fire to get it out of the quarry. 

 The king farms it every year to some merchant, 

 who carries provisions for the workmen for that 

 space of time." 



This precious substance, if we judge from its 

 hardness, cannot be the present article; but is 

 probably that beautiful jad (though perhaps fu- 

 ture discoveries may impose a different name), 

 which is brought from Tibet and China in the 

 form of small basins, sword-handles, c. It some- 

 what resembles chalcedony, but is far more pond- 

 erous. The chemical analysis and proper classi- 

 fication of this singular substance remain among 

 the desiderata of mineralogy, though specimens be 

 not uncommon in various great collections. 



MODE VII. ARGILLACEOUS INTRITE. 



The argillaceous intrites and glutenites are of 

 prodigious extent and importance. The chief 

 intrite, commonly called clay porphyry, as con- 

 sisting of crystals of felspar in a base of clay, is 

 sometimes a principal material in vast chains of 

 mountains. The argillaceous glutenites, called 



