Argillaceous Genus: 91 



That from Hollington, near Utoxeter^ is of a 

 whitiih or yellowifh grey, and its fpecific 

 gravity 2,288. That from Kniperjly, in. Staf- 

 ford/hire, is of a bluifh grey, and fo infufible 

 as to be ufed for a fire-ftone : its fpecific gra- 

 vity is 2,568- 



SPECIES X. 



Argillaceous Earth intimately mixed 'with 1,7 

 of its weight of Sikx, about 0,7 of its 

 weight of mild Magnefia^ 0,09 of its 'weight 

 of mild Calcareous Earth> and about its own 

 weight of Jemlfhlogifticated Calx of Iron. 



Jlorn-ftone, Hornblende of Cronfted 9 and Tal- 

 cum Striatum of Rinnan, Mem. Stockh. 1 754, 



The general characters of this ftone, be- 

 fides a partial folubility (though without ef- 

 fervefcence) in acids, and a hardnefs never 

 fufficient to ftrike fire with fteel, properties 

 which are common to it with the former fpe- 

 cies,) are i ft> a fpecific gravity never lefs than 

 2,66, and frequently rifing to 3,88. 2 d * a 

 ftrong earthy fmell which it exhales on being 

 breathed upon, or having hot water poured 

 on it : 3 d * a toughnefs or vifcidity perceived 

 in pounding it in a mortar, like mica or horn, 

 from whence it derived its name: 4 th * its af- 

 fording a greenifh grey powder when pound- 

 ed ; 



