CLA SSIFICA TION OF IGNEO US R O CKS 629 



cases it is proposed that the name of the mineral be given fol- 

 lowed by the word -bearing. So the cases just mentioned would 

 be quartz-bearing or nephelite-bearing persalane and dosalane 

 respectively. Such names indicate only that the rocks belong 

 to these Classes and carry quartz or nephelite, with no implica- 

 tion of their other characters. 



TEXTURE. 



As already explained, the texture of a rock is to be expressed 

 in the nomenclature by a qualifying term applied to the name 

 of the magmatic unit, and connected with it by a hyphen. 



There are now in use terms expressing some of the com- 

 monest and most characteristic textural features of igneous 

 rocks. It is proposed to use these in their present form, or to 

 modify them by abbreviation in some cases with the addition of 

 syllables indicating the degree of granularity. The syllable -0 

 is added to indicate that the texture is recognizable megascop- 

 ically ; -i is added when it is microscopic. For example : 



Granitic = xenomorphic and hypautomorphic granular ; grano — mega- 

 scopically granitic, megagranitic ; grani = microscopically granitic, micro- 

 granitic. 



Trachytic = panautomorphic with tabular feldspars ; tracho = mega- 

 scopically trachytic, megatrachytic ; trachi — microscopically trachytic, 

 microtrachytic. 



Graphic — pegmatitic = granophyre in the Rosenbusch sense ; grapho 

 = megagraphic ; graphi = micrographic. 



Poikilitic ; poikilo = megapoikilitic ; poikili = micropoikilitic. 



Ophitic ; ophito — megophitic ; ophiti = microphitic. 



Fehitic — aphanitic ; felso = megafelsitic ; felsi = microfelsitic, micro- 

 scopically homogeneous, but not isotropic glass. 



Vitreous ; vitro — megascopically vitreous ; vitri = microscopically vit- 

 reous. 



Spherulitic ; sphero = megaspherulitic ; spheri — microspherulitic. 



Porphyritic ; phyro = megaporphyritic ; phyri = microporphyritic, that 

 is, the phenocrysts are not megascopically notable, or are quite insignificant. 



With the term phyr may be combined one indicating the tex- 

 ture of the groundmass as follows : 



Porphyritic granitic; granophyro = megagranitic, megaporphyritic; 



