MODE I. TALC. 30 1 



MODE I. TALC. 



Of this beautiful substance, considered as a Distinctions, 

 rock, there are two principal structures : the 

 COMMON talc, which occurs in translucent Common, 

 leaves, sometimes as large as four or five feet in 

 diameter, and which chiefly comes from the 

 Uralian mountains of Russia, whence it is called 

 Muscovy talc; and what may be called MASS- 

 IVE talc, consisting of minute scales, irregularly 

 '-agglomerated, as in the substance called the 

 chalk of Briancon, which, from its farinaceous 

 decomposition, and other circumstances, cannot 

 justly be regarded as a soft steatite, but must 

 belong, on the contrary, to this division. It 

 must at the same time be remarked, that the 

 deficiencies of all our mineralogic systems, con- 

 cerning so common a substance as talc, are not 

 a little surprising. The grave and profound 

 Walleri us justly confines the appellation of talc 

 to the two substances above mentioned ; but the 

 science has continued to suffer by the confusion 

 of two very distinct branches, petralogy and 

 lithology, every minute substance found in a 

 vein, or parasitic, disturbing the attention from 

 the grand features of nature. The magnesian 



