MINERAL SUBSTANCES. 13 



other elements, and others still are found in both condi- 

 tions. I will give some examples of each. Some of the 

 noble metals (so called), as gold and platinum, are never 

 found combined with any other element. On the other 

 hand, the metals potassium, sodium, calcium, magnesium, 

 aluminum, and ammonium are never found uncombined. 

 Silver, copper, and mercury are among the examples of 

 metals that are found in their simple state, or, as it is 

 commonly expressed, found native, and also combined 

 with other elements, as sulphur, oxygen, etc., in the form 

 of ores. While oxygen is, in its simple state, in the mix- 

 ture which we call air, it also appears in combination 

 with almost all the elements, and forms from one third 

 to one half of the crust of the earth. Hydrogen, which 

 is so abundant as one of the elements of water, is never 

 found uncombined. The same may be said of chlorine, 

 one of the elements of common salt. Sulphur and car- 

 bon are both found native as well as combined, but phos- 

 phorus is always in combination. 



10. Minerals that Contain Many Elements. There is 

 very great difference in degree in the compound char- 

 acter of the minerals found in mineralogical cabinets. 

 While there are many of those compounds which were 

 brought to your notice in Part II. oxyds, sulphurets, 

 salts, etc. there are also many which are much more 

 compound than these. The only approach made to such 

 complex compounds by the processes of chemistry is in 

 the double salts, such as alum, and the tartrate of anti- 

 mony and potash. As examples, I mention mica, called 

 isinglass by the common people, which is composed of 

 silica, alumina, oxyd of iron, fluoric acid, and water ; and 

 that splendid mineral, so much used for making costly 

 vases and other ornamental articles, lapis-lazuli, which is 

 composed of silica, alumina, soda, lime, iron, sulphuric 

 acid, sulphur, chlorine, and water. 



11. Mixtures of Compounds in the Rocks. In many 

 of the rocks there are mixtures of the mineral compounds. 



