Merrill and Packard — Azure blue Pyroxenie Rock. 279 



This alnoite from Ste. Anne differs from the original alnoite 

 from Alno, in containing much more olivine and in being free 

 from plagioclase, a mineral which can be frequently observed 

 in sections of the Alno rock. Otherwise they resemble one 

 another very closely. Although there is no way of ascertain- 

 ing the age of this dike it is probably connected with the 

 great volcanic center at Montreal which constitutes the eleva- 

 tion known as Mount Royal, from which the city takes its 

 name. This is formed of a theralite, cut through by a later 

 eruption of ekeolite syenite, both rocks breaking through and 

 altering the Trenton limestone of the vicinity, the whole being 

 traversed by several series of dikes, tinguaites, bostonites and 

 other rocks to which a definite name cannot at present be given 

 but which probably originally held some melilite although they 

 are now as a general rule much altered. Dr. Harrington has 

 been for several years collecting material and data for an accu- 

 rate description of the whole complex and we hope before 

 long to have the work sufficiently advanced for publication. 

 The present paper may be considered as a first contribution 

 toward an accurate knowledge of these rocks. 



McGill University, Montreal. 



Art. XXXI Y. — On an Azure-blue Pyroxenie Pock from, 

 the Middle Gila, JVeio Mexico ; by George P. Merrill 

 and R. L. Packard. 



Among- a lot of ores and other materials donated to the 

 Museum some months ago by Prof. J. H. Huntington then at 

 Silver City, ]STew Mexico, was a hand specimen of a finely 

 saccharoidal rock of a beautiful light azure-blue color with 

 spots of serpentine, and which was stated to have come from 

 a point on the Gila River some 40 miles west of that city. 

 The striking beauty and color of the rock at once excited our 

 interest, and arrangements were made for analysis and micro- 

 scopic study. Meanwhile business called Mr. Merrill to Silver 

 City, and while there he took pains to visit the locality and 

 learn for himself the source and geologic character of the rock. 

 The results of our combined investigations are given in the 

 following notes. 



In the field the rock was found to occur in sporadic nodular 

 masses of rarely 100 pounds weight, imbedded in a granular 

 crystalline serpentinous limestone which in the form of a nar- 



Am. Jour. Sol— Third Series, Vol. XLIII, No. 256.— April, 1892. 

 18 



