258 F INLAY 



cooling in magmas which arc of medium percentages in sihca, 

 and contain large amounts of alumina and the alkalies, with low- 

 iron, lime and magnesia, has thus far been reported from but 

 few localities in North America. It is found at Montreal, and 

 in the county of Dungannon, Ontario, Canada ; near the town 

 of Litchfield, in Maine ; on Salem Neck, and at Marblehead, 

 in Massachusetts. It is met with at Red Hill, New Hampshire. 

 A great dike-like mass occurs near Beemerville, New Jersey. 

 Nephelite syenite has a large development near Magnet Cove, 

 Arkansas, and the rock has likewise been described from Crip- 

 ple Creek, Colorado, and from the trans-Pecos region of west- 

 ern Texas. Lawson's nephelite-pyroxene-malignite from the 

 Rainy River district, Ontario, Canada, is a nearly related type. 

 Similar occurrences of nephelite syenite and related rocks have 

 been reported from the provinces of Sao Paulo, Rio de Janeiro, 

 and Minas Geraes in lirazil by Derby. 



The San Jose nephelite syenite is remarkable for its uniform 

 character over large stretches. In the region studied it has not 

 been split up into widely separated types such as are usually 

 found where similar magmas have consolidated. Over nine 

 tenths of the San Jose district it is a medium-grained, light or 

 dark gray rock resembling granite. It is leucocratic and dull- 

 looking by reason of the oily luster of the nephelite contained 

 in it. The i)risms and aggregates of the ferro-magnesian min- 

 erals are jet black, sharply outlined and in strong contrast with 

 the lighter feldspars. Honey yellow, lozenge-shaped crystals 

 of titanite are always found. Jt is only rarely that portions of 

 the mass where the .single crystals are locally developed in large 

 size are observed, but individuals of orthoclase are sometimes 

 an inch and a half in length ; in other localities the basal sec- 

 tions of hornblende are three quarters of an inch in diameter, 

 and rectangular masses of nephelite may be half as long again. 



IMack fine-grained basic segregations, like the knots in gran- 

 ite, are characteristic of certain lirnitecl tracts where they are so 

 numerous as to give the nephelite syenite a mottled appearance. 

 They are at times elliptical and again angular, and are found in 

 all sizes up to five or six inches. They may be arranged in 



