ORDER v. PRISMATIC TALC-MICA. 1Q5 



Sectile, in a high degree. Thin laminae are easily 

 flexible. Hardness = 1-0... 1-5. Sp. Gr. =2-713 

 a dark-green variety, compound of large indi- 

 viduals. 



Compound Varieties. Imperfect globules and 

 stellular groupes : composition imperfect columnar. 

 Sometimes several crystals are engaged with each 

 other, so as to produce conical and cylindrical ag- 

 gregations. Massive : composition granular of va- 

 rious sizes of individuals, often impalpable ; some- 

 times imperfect columnar. The individuals are 

 sometimes strongly coherent with each other, or flat, 

 so as to give rise to an imperfect slaty structure. 

 Often earthy, without connexion of its particles. 



OBSERVATIONS. 



1. The difference among the species and sub-species, 

 comprehended within prismatic Talc-mica, depends upon 

 various properties at the same time, both of the individuals 

 themselves and of their compositions, and it is not there* 

 fore without many difficulties. The varieties of dark- 

 green (leek-green, celandine-green, &c.) colours, inclining 

 to brown, constitute the Chlorite, subdivided into foliated 

 and common, slaty and earthy Chlorite. The first of these 

 contains the crystallised varieties, and such compound ones 

 as consist of easily separable individuals, not presenting a 

 slaty structure. The second contains those granularly 

 compound varieties, in which the individuals can scarcely 

 be traced, or in which they are not observable at all. 

 Chlorite-slate, or slaty Chlorite, refers to such compound 

 varieties as have a slaty texture, and earthy Chlorite to 

 such as are but loosely coherent, or already in a state of loose 

 scaly particles; and it is distinguished from foliated Chlo- 



