96 The Paragenetic Relations of Minerals. 



clase* (perhaps always accompanied by peg- 

 matolite, and surrounding it in a wreathlike 

 manner), tetartine, labrador, spodumene, epi- 

 dote, disthene, garnet, zirkon, beryl, tourma- 

 line, topaz, chrysoberyl, titanite (when this 

 mineral occurs, the granite is always very 

 poor in mica), pyrochlor, magnetite, cassiterite, 

 ilmenite, spessartite, specular iron, iytteroil- 

 raenite, mengite, columbite, tantalite (always 

 accompanied by the prior formed beryl), aeschy- 

 nite, orthite, gadolinite, euxenite, iron pyrites, 

 graphite. 



The occurrence of molybdanum glance has also been re- 

 corded, although it probably occurs only in fissures. No kind 

 of rock presents such an abundance of accessory minerals as 

 granite. Some which, like corundum, arsenical pyrites, gold, 

 &c, are questionable, have not been enumerated. 



Syenite. — This rock, consisting essentially offelsite-mikro- 

 line, pegmatolite or labrador, and black amphibole, has been 

 frequently confounded with gabbro and hypersthene rock, 

 when the amphibole was regarded as pyroxene. Syenite has 

 probably been formed at a somewhat lower temperature than 

 dolerite, diabase, nepheline rock, basalt, &c, as the formation 

 of amphiboles does not require so high a temperature as the 

 pyroxenes, with the exception of spodumene. Most of the 

 accessory minerals contained in syenite occur also in granite, 

 and these rocks are sometimes seen to pass into each other. 



Besides those modes of occurrence of minerals already 

 spoken of, as indicating, in the greater number of instances, 

 some sort of segregative formation, there are others which 

 resemble them in this particular, although presenting differ- 

 ent petrographic features. Among these are the masses of a 

 mineral, or most frequently of several minerals, which may 

 be essential constituents, or accidental admixtures, of the 

 rock in which they are imbedded. The outlines of these 

 masses are not very well defined, but they are remarkable 

 for the perfect character of the minerals which compose 

 them. Some few present a considerable resemblance in one 

 particular, — the mineral species — occurring with masses of 

 primitive limestone (Kalkstoeken); and, notwithstanding other 



* Apparently a much more frequent mineral than was hitherto supposed. 



