YELLOW EARTH. 187 



straight slaty in the great, fine splintery in the 

 small. 



Faintly glimmering, almost dull. Colour greenish- 

 grey, mountain-, asparagus-, oil-green. Streak 

 greyish-white. Translucent on the edges. 



Not particularly brittle. Said to be soft in a low 

 degree. (It is sometimes as hard as rhombohe- 

 dral quartz). Sp. Gr. =; 2-722, KIRWAN. 



Whet-slate is a slaty rock, containing a great proportion 

 of quartz, in which the component particles (the same as 

 in clay -slate, mica-slate, and gneiss, but in different relative 

 quantities) are so very small, as to withdraw themselves 

 from observation. This may serve for explaining on one 

 hand the passage of whet-slate into clay-slate, on the other 

 hand the employment it allows for grinding, which is im- 

 possible in any mineral that in reality is soft. Whet-slate 

 occurs in beds between clay -slate, particularly in the older 

 rocks ; and the varieties best adapted for use are found at 

 Sonnenberg in Meinungen, and at Probstzelle and Lichte- 

 tanne in Saalfeld. They are likewise brought from the 

 Levant. Less useful or fine grained varieties are found in 

 many countries. The varieties from the neighbourhood of 

 Liege, Argile schisteuse novaculaire of HAUY, are not compre- 

 hended among the whet-slate of WEBNER. They consist 

 of two layers of stone of different colour and composition, 

 one of them being yellowish-grey and very fine grained, 

 the other reddish-brown and coarser. The use of whet- 

 slate as a grinding material is sufficiently known. 



YELLOW EARTH. 



Yellow Earth. JAM. Syst. VoL II. p. 81. Man. p. 312. 

 Massive. Composition impalpable. Principal frac- 



