98 BOOKS POEMBI) THROUGH IGNEOUS AGENCIES 



bear the mineral nepheline in place of feldspar. Based upon the 

 presence or absence of olivine, we have, first, nepheline hasalt^ 

 and second, nephelinite^ The name nepheline dolerite has been 

 given in some cases to the coarser, holocrystalline, olivine-bearing 

 varieties. 



Like the leucite rocks, the members of this group are some- 

 what limited in their distribution. 



