19 13.] ROGERS— THE NOMENCLATURE OF MINERALS. 607 



nomenclature like that now used for plants and animals was at one 

 time used for minerals. In the first (1837) and second (1844) edi- 

 tions of Dana's " System of Mineralogy " binominal names* were 

 given along with the usual names, mostly ending in -ite. Thus barite 

 was known as Baralus ponderosus and celestite as Baralus prismati- 

 ciis. The genus Baralus also included witherite, strontianite, and 

 barytocalcite. Classes and orders were also recognized. The classi- 

 fication used then was the natural history classification of Werner 

 and j\Iohs based upon external characters. 



This gradually gave way to the chemical classification of Berze- 

 lius and the Swedish chemists. In the third edition (1850) of 

 Dana's " System " the chemical classification was adopted and the 

 binominal names, even as synonyms, were rejected. 



A mineral species is a mineral with definite chemical composition 

 and distinctive crystal form (or crystalline structure). "Definite" 

 must be interpreted in the light of isomorphism, including mass-efifect 

 isomorphism first recognized by Penfield.^ It is also necessary to 

 recognize solid solutions of a kind different from isomorphism.^* 

 Pyrrhotite,® for example, is a solid solution of sulfur, S, in 

 ferrous sulfid, FeS. Nephelite,'^ is a solid solution of NaAlSi04, 

 KAlSiO^ and NaAlSisOg, of which only the first two are isomor- 

 phous. 



Crystal form must also be used in defining a mineral species for 

 polymorphous minerals are distinct and are often strikingly differ- 

 ent in physical properties as in the extreme case of diamond and 

 graphite. Some of the dimorphous minerals have distinctive names 

 (e. g.^ calcite, aragonite) but there is a tendency to use a prefix be- 

 fore the first known mineral for the dimorphous form. Thus we 

 have clinozoisite, paralaurionite, pseudowollastonite, metaboracite, 



* These binominal names were first suggested by Dana in an article in the 

 fourth volume of the Annals of the New York Lyceum. 



^ That is, in large molecules dissimilar elements or groups may replace 

 each other. See Amer. Jour. Sci. (4), Vol. 7, p. 97, 1899. 



5a- Kiister {Zeit. fiir phys. Cliem., Vol. 17, p. 367, 1895) maintains that a 

 distinction should be made between solid solutions and isomorphous mixtures. 



^ Allen, Crenshaw, and Johnston, Amer. Jour. Sci. (4), Vol. Z3, P- I93, 1912. 



"^ Bowen, Amer. Jour. Sci. (4), Vol. Z2i, P- 4Q. 1912. 



PROC. AMER. PHIL. SOC. , LII. 212 U, PRINTED NOV. l8, I9I3. 



