602 MINERALS AND VEINS OF ^EGIRINE-SYENITE, 



appear red-brown in colour, due to much distributed iron-oxide. 

 This iron oxide is derived in part from the decomposition of 

 secondary ferrous silicates, vestiges of which, as minute acicular 

 crystals of a light bluish-green colour, yet remain. In other- 

 parts, patches of chlorite are developed. An interesting radial- 

 fibrous mineral is developed amongst the decomposition products 

 of the large veins; the aggregates are very tiny and spherical, 

 light yellow to reddish-yellow, and have a high double refraction. 



Carbonation of the ferriferous silicates has led to the develop- 

 ment of much siderite accompanied by small quantities of calcite. 

 The siderite forms perfectly idiomorphic rhombs and is attacked 

 by dilute hydrochloric acid only after warming, thereby readily 

 distinguishing it from calcite. Where decomposition has been 

 effected in the presence of insufficient carbon dioxide, the carbon- 

 ates are deeply stained by hydrated iron and manganese oxides. 

 Amongst the materials of some of these carbonate paramorphs, 

 and in rare instances scattered through the more indefinite 

 siliceous products of the metachemisation cycle, are minute stain- 

 able areas thought to probably imply the presence of Analcite or 

 some nearly related mineral. 



Fluor is found constantly in tiny violet grains amongst the 

 carbonates developed from the arfvedsonite, and in large isometric 

 forms occup} 7 ing positions amongst the secondary siliceous fillings. 



Titanite — Some of the sections contain very numerous frag- 

 ments of a highly refracting and doubly refracting mineral, 

 chiefly appearing in the wedge-shaped form typical of this 

 mineral. The individuals are very tiny. They have been noted 

 to occur in connection with highly altered felspar, commonly in 

 chalcedony fillings, and in one instance forming a fringe around 

 a perofskite crystal embedded in chalcedony. 



Leucoxene in pseudomorphic areas after ilmenite. 



iv. Summary and Conclusions. 



The veins occupy one-time fissures, some of which were very 

 local, extending only a few inches; others were continuous by the 

 development of connections between a series of these minor 



