24 TERMINOLOGY. . 25. 



pound minerals from these considerations. It is necessary, 

 however, to distinguish correctly between the simple and 

 the compound minerals; and since this cannot be done 

 otherwise, than by knowing all the details respecting these 

 bodies themselves, their consideration must not entirely be 

 neglected. 



The union among the simple minerals in the mixed mi- 

 neral, is sometimes so close, and the particles of the mixture 

 so diminutive, that it becomes impossible to ascertain their 

 reality by simple ocular inspection. Many Mineralogists 

 in this case consider mixed minerals as simple, and clasa 

 them as such in their systems. But this is not the only 

 error of the kind, occurring in such arrangements. Both 

 mixed and decomposed minerals are by themselves no 

 longer objects of the method ; yet there are even mixtures 

 of decomposed minerals, which have been introduced into 

 the systems, and to which particular places have been 

 assigned. 



Examples of mixed minerals we have in many varieties 

 of rocks ; in granite, gneiss, porphyry, &c. ; also in many of 

 those masses which constitute beds and veins. Examples 

 of close or impalpable mixtures, are found in Iron-flint 

 and Heliotrope, both varieties of rhombohedral Quartz ; 

 the first of which is mixed with oxide of iron, the other 

 with Green Earth, a variety of prismatic Talc-mica. Mix- 

 tures of decomposed minerals we have in Clay, Yellow- 

 Earth, Tripoli, &c. 



. 25. DIVISION OF THE NATURAL-HISTORICAL 

 PROPERTIES. 



The natural-historical properties of minerals are 

 divided into ; 1. such as refer to simple ; 2. such 

 as refer to compound minerals ; 3. such as are 

 common to both. 



The natural-historical properties of minerals compre- 

 hend their colour, the different degrees of hardness, the 



