HANDBOOK FOR THE DEPARTMENT OF GEOLOGY 557 



Brazil) is tbe name applied to a similar rock iu which hornblende or 

 augite prevails in place of mica. These rocks are placed by Prof. 

 Roseubusch in his latest work iu the group of syenitic lamprophyrs. 

 Monzonite is a varietal name for the augite syenite of Monzoui in the 

 Tyrol (specimens 36300 and 73112). 



The distribution of the syeuites is much more limited than is that of 

 the granites. The following localities and varieties are now represented 

 in the exhibition series : 



Hornblende syenite: Marblehead Neck, Massachusetts, 35962; Red Hill, Moultoubor- 

 ougli, New Hampshire, 29580; Blue Hills, Custer County, Colorado, 36881 ; Cluro 

 Hills, Cortes Range, Nevada, 21288; Serra de Stinba, province of Babia, Brazil, 

 69857 and 69858; Vosges Mountains, Germany, 36289; Biella, Piedmont, Italy, 

 36287; Oslo, Christiana, Norway, 36288 ; Ise, Japan, 11727; near Dresden, Moritz- 

 berg, Zischeuwitz, and Meissen, Saxony, 3861, 3863, 36285 and 36286. 



Augite syenite: Jackson, New Hampshire (Uralitic), 27909 and 29587 ; Monzoni, Tyrol 

 (Monzonite), 36300 and 73112 ; Ilha do Cabo Frio, Rio de Janeiro, Brazil, 69934 

 and 69936; Serra do Hilario, province of Sao Paulo, Brazil (Vogesite), 70025. 



Mica syenite : Schriesheim, Odenwald, Germany (Minette), 36293; Mittersbausen, 

 Odenwald, Germany, 36290; Nassau, Germany, 36296 ; Weinheim, Baden (Min- 

 ette), 36291; Cleurz, in the Vosges Mountains, 36292; Spessburg, near Barr in 

 the Vosges Mountains, 36225; Andlauthal, in tbe Vosges, 36294; Scbarpensteiu 

 and St. Michaels, Saxony (Minette), 36297 and 36298; Scbnappenhaussuer, in the 

 Fitchtelgebirge (Lamprophyr of Gurubel), 36299; Gallatin and Jefferson Coun- 

 ties, Montana, 38600, 73168, and 73169. 



Syenite porphyry : Near Alteuberg, Saxony, 3871; St. Nabord, in the Vogeseu, 73120. 



3. The nepheline (et^olite) syenites, foyaits. 



Nepheline from the Greek vecpelyj, a cloud, since the mineral becomes 

 cloudy on immersion in acid. Elseolite from eXaiov, oil, in allusion to its 

 greasy luster. Syenite from Syene iu Egypt. 



Mineral composition. — The essential constituents of this group are 

 nepheline (elseolite) and orthoclase, with nearly always a pyroxenic 

 mineral and a plagioclase, feldspar. The common accessory minerals 

 are sphene, sodalite, cancrinite, zircon, apatite, black mica, and the iron 

 ores (ilmenite and magnetite) with occasional eucolite, melinophane 

 (specimens 36339 and 363 10), and also tourmalines, perowskite, and oli- 

 vine. Calcite, epidote, chlorite, analcite, aud sundry minerals of the 

 zeolite group occur as secondary products. 



Chemical composition. — The composition of the elseolite syenite from 

 province of Algrave, Portugal, as given by A. Meriau, is as follows : 

 Silica 54.61, alumina 22.07, sesquioxide of iron 2.33, protoxide of iron 

 2.50, magnesia 0.88, lime 2.51, soda 7.58, potash 5.46, water 1.13, ti- 

 tanic oxide 0.09, phosphoric acid 0.15 per cent. 



Color. — The colors are light to dark gray and sometimes reddish. 



Structure. — These, like the syenites and granites, are massive holo- 

 crystalline granular rocks, and as a rule sufficiently coarse in texture 

 to allow a partial determination of the constituent parts by the unaided 

 eye. In the Litchfield (Maine) syenite the elseolite often occurs in 

 crystals upwards of 5 centimetres in length, and zircons 2 centimetres in 



