PLAGIOCLASE ROCKS. 



COMPOSITION. 



LOCALITIES. 



Drachenfels 

 trachyte 



Granular matrix of sanidine and 

 oligoclase, with magnesia mica 

 and hornblende, and large crys- 

 tals of sanidine. May contain 

 tridymite. 



Minette, or A grey felsitic matrix of ortho- 

 mica syen- clase, with much mica, and 

 ite sometimes crystals of augite or 



hornblende; chiefly in veins and 



dykes. 



Drachenfels, near Kb'nigs- 

 winter, on the Rhine ; and 

 other localities in the Sie- 

 bengebirge. 



In the Channel Islands. Near j 

 Framont in the Vosges, near ! 

 Oederan in Saxony, and in j 

 the Lake district, at Sale | 

 Fell west of Bassenthwaite, 

 and Cross How Beck. 



Miascite 



Phonolite 



Granular crystalline mixture of , Miask, Ditro 

 orthoclase, nepheline, sodalite, yania. 

 and biotite. 



in Transvl- 



Compact rock, rings under the 

 hammer, weathers white like 

 felsite. The matrix consists of 

 sanidine, nepheline, hornblende, 

 titanite. Crystals of sanidine 

 occur more developed. Some- 

 times oligoclase is a constituent. 

 Occasionally vesicular and amyg- 

 daloidal. 



Wolf Rock. Mileschauer in I 

 Bohemia, Aussig in Bohe- i 

 roia. Forms conical isolated 1 

 hills in the Mittelegebirge i 

 of Bohemia ; in the Auvergne, 

 as at the Roche Sanadoire. 



Family of Quartz-bearing Plagiodase Rocks. 



These rocks are as distinct from the ordinary plagioclase rocks, as 

 are quartz orthoclase rocks from the quartzless series, but they are 

 less frequently met with. 



NAME. 



COMPOSITION. 



LOCALITIES. 



Quenastite or j A granular compound of quartz, 

 Quartz-dio- plagioclase and hornblende, with 

 rite orthoclase in some localities. 



Quartz- | A micro-crystalline green paste 



propylite j of quartz, oligoclase and horn- 

 ! blende, with larger crystals of these 

 minerals and titaniferous iron. 



Dacite or Grey or brown granular or com- 

 Quartz-ande- pact matrix of felspar and horn- 

 site blende, with quartz, oligoclase, 

 sanidine, and hornblende in fine 

 grains or crystals, with magne- 

 tite. 



Quartz- j A micro-crystalline compound of 



dolerite j quartz, plagioclase, augite and 

 i olivine. 



Quenast in Belgium, Catau- 

 zara in Calabria. In the 

 Tonale Pass in the Tyrol is 

 a micaceous quartz diorite. 



Many places in the U.S., such 

 as Papoose Peak, Hills of 

 Golconda, &c., and some 

 places in Hungary. 



Named from the ancient 

 Dacia ; found in Transyl- 

 vania and Hungary. 



U.S.A., on the Upper Snake 

 River and Shoshone Mesa. 



