INTRODUCTORY OBSERVATIONS. 



. 17. PROPERTIES OF MINERALS. 



The properties, or characters of minerals may be said to* 

 be of two kinds : the first consisting of those which miner- 

 als exhibit while in their natural state ; and the second of 

 those observed during, or after a change has been produ- 

 ced in their nature. The former of these are termed Nat- 

 ural characters ; the latter Chemical characters. 



The natural characters comprehend their color, different degrees 

 of hardness and transparency, the kinds oflustre, the regular forms, 

 the various sorts of aggregation under which compound minerals 

 exist, the specific gravity and taste of minerals. The chemical 

 characters are those whose use effects the decomposition of a min- 

 eral, or which induce an obvious alteration in its state ; of this kind 

 are the fusibility of minerals, or their behavior before the blowpipe, 

 their solubility in acids and the accompanying phenomena, phos- 

 phorescence by heat, and chemical analysis with a view to learn the 

 quality of the composing ingredients and the order in which they 

 are present. 



The natural characters only, are employed either in the Descrip- 

 tion or Characteristic of the science. The chemical characters ap- 

 pertain to Chemistry, and require to be enumerated and explained 

 in a mineralogical work, merely to render intelligible the results of 

 Chemistry, which are appended to the descriptions of minerals, with 

 the design of enlarging, as far as possible, our knowledge of these 

 bodies. 



. 18. DIVISION OF THE NATURAL PROPERTIES. 



The natural 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 first division will consist of those which can be observed only 

 in an individual itself, or in a fragment of an individual. To such 

 belong the geometrical properties, or such as refer to space ; the 

 relations of structure, of surface, and the phenomena of refraction. 

 The second division embraces the relations of composition, the 



