268 TERMINOLOGY, . 189. 



The columnar and lamellar particles are exactly in the 

 same case. The columnar particles may still very easily be 

 traced in the stalactitic and reniform shapes, called brown 

 Hematite. But in compact brown Iron-stone, they have 

 entirely disappeared. Of this vanishing arid impalpable 

 composition, we have a very remarkable example in those 

 varieties of rhombohedral Quartz, which have been called 

 Calcedony, and occur in reniform and stalactitic shapes. 

 Commonly there is not a trace of their composition left 

 in the interior ; but in some of its varieties this com- 

 position is still observable. Among these, the fibrous 

 Carnelian is one of the most well known instances. 



It has been mentioned above (. 171. 172.)? that the co- 

 lumnar composition has sometimes been confounded with cer- 

 tain relations of structure. Fibrous fracture is always colum- 

 nar composition ; and the difference between what has been 

 called the foliated and the radiated fracture, consists in no- 

 thing else but that the first refers to simple minerals or gra- 

 nular compositions, while the second is confined to columnar 

 compositions. 



. 189. SINGLE AND MULTIPLE COMPOSITION. 



The single composition takes place, if a com- 

 pound mineral consists of individuals ; but if the 

 particles of composition are again composed, then 

 the composition is multiple. 



The compositions treated of in the preceding paragraphs, 

 are single compositions. 



But there exist granular particles of composition, which 

 are again composed of granular particles ; and these only 

 are real individuals. They join into those masses, which 

 again on a larger scale produce a. granular composition. 

 Macrotypous Lime-haloide exhibits examples of this com- 

 position. Sometimes the granular particles consist of co- 

 lumnar particles, diverging from the centre, or from one of 



