Washington — Suggestion for Mineral Nomenclature. 137 



Art. XV III. — A Suggestion for Mineral Nomenclature • by 

 Henry S. Washington. 



Introduction. — That the science of mineralogy may be 

 regarded as a branch of descriptive chemistry (but one which 

 deals only with substances occurring in nature) is recognized 

 in the prevalent mineral classifications, where the chemical 

 composition is the primary and most important factor. The 

 character of the negative (acidic) ion controls for the for- 

 mation of the largest classes, and subclasses may be based on 

 the character of the positive (basic) ion, in some cases preceded 

 by separation into anhydrous and hydrated compounds. In all 

 these subclasses minerals which belong to the same acidic type 

 are placed together. The ultimate smallest groups, which 

 bring together minerals regarded as most closely related, are 

 based on similarity in crystal form, dependent on isomorphous 

 replacement, either entire or partial, and either in the negative 

 or the positive portion of the molecule; while again dissimi- 

 larity in crystal form due to polymorphism of substances with 

 the same empirical chemical composition, serves to distinguish 

 between groups chemically alike. 



The crystal form, therefore, is a necessary diagnostic, as 

 important for the formulation of our idea of any mineral as 

 its chemical composition. As Miers* expresses it, for the defini- 

 tion of minerals "we are forced to employ at least two proper- 

 ties, namely the chemical composition and the crystalline 

 form: these two, when completely known, are necessary and 

 sufficient for the definition and determination of any mineral." 

 The less important characters, such as color, structure, habit, 

 state of aggregation, and minor details of chemical composition, 

 are (or should be) used only to distinguish very subordinate 

 (varietal) divisions, and, as Miers justly says, far too much 

 importance has been generally assigned to them in naming 

 minerals. Many cases will also occur to every mineralogist 

 of minerals which stand alone and can only be referred to 

 indefinite positions in the classes, dependent on the general 

 character of the negative ion ; that is, they show no intimate 

 relations with other minerals through both their chemical and 

 crystallographic characters and constitute the sole represen- 

 tatives of potential groups, which thus correspond to the mono- 

 typic genera of botany and zoology. 



In this necessary utilization of both chemical composition 

 and crystallographic characters, the definition and classification 

 of minerals differ from, and may justly be considered as in 



*H. A. Miers, Mineralogy, London, 1902, p. 2. 



Am. Jour. Sci.— Fourth Series, Vol. XXXIII, No. 194.— February, 1912. 

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