340 DIIAKE — THE GEOLOGY OF IXDIAX TERRITORY. [Sept. 3, 



mottled appearance. In the red* color are blended a light pink and 

 also deeper ^ed, due to the feldspar crystals, which are red and 

 form by far the larger part of the rock. The black specks are 

 small magnetite crystals. Associated with the black crystals are 

 greenish hornblende and chlorite crystals, which give a greenish 

 tint hardly noticeable on a casual observation. It contains also a 

 few small white quartz crystals. The crystals composing the rock 

 vary in size from those which give a general granular appearance 

 to the ground mass to feldspar crystals that are i c. m. or more in 

 length. The freshly broken rock shows a general fine-grained, 

 somewhat shiny and bright appearance with numerous shining 

 crystal faces of the larger feldspars. 



Microscopic Examination. — Feldspars, quartz, chlorite and mag- 

 netite are the principal minerals of the rock, while hornblende and 

 epidote occur sparingly. A holocrystalline texture is shown 

 throughout the rock. The most striking and general microscopic 

 feature is its granophyric and micropegmatitic texture. Through 

 most of the orthoclase crystals quartz is intergrown in the most inti- 

 mate manner, so that each feldspar shows radiating or parallel alterna- 

 ting quartz and feldspar in narrow bands, which form fan-shaped or 

 irregular patches. In other cases, the quartz appears m trian- 

 gular sections along lines through the feldspar crystals, or is micro- 

 pegmatitic. In any given feldspar crystal, the included quartz 

 plates or prisms show the same orientation. Quartz occurs spar- 

 ingly isolated in larger crystals, but very rarely shows its out- 

 lines. Feldspars are the predominant minerals. They are princi- 

 pally orthoclase, but plagioclase feldspars are of rather common 

 occurrence. The feldspars have a fine granular appearance and a 

 reddish color. Phenocrysts of feldspar are quite common ; they, 

 however, generally show irregular outlines instead of crystal faces. 

 Magnetite occurs in small opaque masses, many of which show per- 

 fect crystal outlines. They show a slight grouping through the rock 

 and in places give a blended appearance to the crystals. 



The hornblende is the greenish variety and of rather uncommon 

 occurrence. The chlorite is common and occurs in greenish bands, 

 spherular aggregates and in minute particles. Epidote is of rather 

 common occurrence. 



