

MINERALOGY. Ill 



account of their hardness, as also their rarity. Precious 

 stones are thus only combinations of silex with other 

 earths, and with the classes ; on the contrary, the ele- 

 mental silices only, viz. the earth-, water-, air- and fire- 

 silices, are massive. 



537. It is here shown, that freedom finds a place also 

 in dead nature. Quartz only is necessary as the earth in 

 general. Its marriages with the other earths, &c., to form 

 precious stones are not necessary, but free or accidental, 

 and may therefore happen for the first time in the labo- 

 ratory. 



538. If we now proceed to the arrangement of the 

 Clay, we find exactly the same law to prevail in the 

 genesis of its minerals i. e. stochiometric combinations 

 with other orders, classes, and elements. We have 

 likewise 



A. Earth-days. 

 Fam. 1. Silicious clays . . Felspar. 



2. Argillaceous clays . Sapphire. 



3. Talcose clays . . Rubv. 



4. Calcareous clays . Epiaotc. 



B. Class-Clays. 



5. Salt-clays . . . Schorl. 



6. Inflammable clays . Azurite. 



7. Ore-clays .... Harmotome. 



V. Elemental-Clays. 



8. Water-clays . . . Clay-slate. 



9. Air-clays .... Potter's-clay, Claystone. 



10. Fire-clays . . . Lavas, Phonolite, loadstone. 



The water-clays are hydrates; the air-clays volatilized 

 hydrates ; the fire-clays are clay fused or transmuted by 

 heat. Here also the first 7 families only are crystallized; 

 the 3 last, on the contrary, as well as the first in part, 

 occur only in a compact state and in large masses. 



539. The Talcs follow the same laws, and we have 



A. Earth-Talcs. 

 Fam. 1. Silicious talcs . . . Mica. 



2. Argillaceous talcs . Sapphirine. 



3. Talcose talcs . . . Talc, Chlorite. 



4. Calcareous talcs . . Augite. 



