Chemical Mineralogy

A mineral may be defined as a naturally occurring substance having a definite chemical composition. The chemical composition of a mineral is the most fundamentally important fact about it, for upon this all its other properties must in great measure be dependent. It should be added that the characters of a mineral depend upon not only the chemical nature of its ultimate particles but both definitely also not the arrangement of these particles in the crystalline structure . The physical characteristics of a mineral may sometimes serve as means of is positive identification, and in the great majority of cases they will be of material assistance, but the final proof of its identity will more often lie in the determination of its chemical character by means of chemical tests. Consequently the study of the chemistry of minerals is the most important single division of the subject. This section will, therefore, be devoted to a brief and elementary discussion of chemical mineralogy. First some general aspects of the subject will be presented, followed by a short description of the methods of testing for the different elements most commonly observed. The scope and size of this site necessitate the assumption that the reader is familiar with at least the essentials of chemical fact and nomenclature.

Scientists up to the present time have established the occurrence of more than eight different elements. The greater part of these, however, is extremely rare and are only of scientific interest. Some forty- four elements are found in sufficient importance, to warrant a discussion of there. A considerable proportion of this list also must be considered as rare in occurrence. The following table gives the names and symbols of the eighteen most common elements arranged in the approximate order of their importance as constituents of the earth’ s crust: .

Oxygen O Sodium Na Phosphorus P Silicon Si Potassium K Sulfur S Aluminiun Al Hydrogen H Barium Ba Iron Fe Titanium Ti Manganese Mn Calcium Ca Carbon C Stontium Sr Magnesium Mg Chlorine Cl Fluorine F

It is to be noted that the above list fails to include such important elements as copper, lead, zinc, silver, gold tin, mercury, nickel, antimony, arsenic, etc., all of which form much less than one hundredth of one per cent of the rocks of the earth’s crust.

These elements occur alone or in various chemical combinations in the form of minerals. Below is given a brief discussion of the various classes of chemical compounds in which the majority of minerals occur.