CLASSIFICATION OF MINERALS. 



751 



Group 4 



II. COMPOUNDS OF THE ELEMENTS. 



The great majority of minerals are compounds of elements. By a 

 comi)Ound is meant that body produced by the combination of two or 

 more elements, and which is different in its nature from and whose 

 pro])erties as a rule are not the mean of those of its constituents. A 

 compound is to be distinguished from a mixture or simple mechanical 

 aggregation in that it always implies a chemical union of its compo- 

 nents, and therefore possesses a definite chemical composition. 



Among minerals the compounds of the elements may be arranged, in 

 accordance with certain chemical laws, under the following heads: 



A. Compounds of the halogens — Huorine, chlorine, bromine, and iodine. 



B. Compounds of sulphur, selenium, and tellurium; also arsenic, anti- 

 mony, bismuth, and germanium. C. Oxygen compounds. D. Com- 

 pounds of organic origin. 



A. COMPOUNDS OF THE HALOGENS— FLUORINE, CHLORINE, BROMINE, 



AND IODINE. 



The halogens — fluorine, chlorine, bromine, and iodine — form simple 

 and complex compounds with other elements. The halides, as these 



