. 190. OF COMPOUND MINERALS. 269 



the corners of the former. Among the first are several va- 

 rieties of rhombohedral Lime-haloide, called Oolite, of he- 

 mi-prismatic Augite-spar, called Actinolite, &c. ; among the 

 second the varieties of several species of Kouphone-spar, 

 of Wood-tin, a variety of pyramidal Tin-ore, &c. In 

 other cases, the granular particles of composition again con- 

 sist of lamellar particles, as in prismatic Hal-baryte and 

 axotomous Kouphone-spar. 



Columnar particles of composition sometimes consist again 

 of columnar ones, as in several varieties of prismatic Iron- 

 ore. The preceding observations will suffice for explain- 

 ing many occurrences of this kind, among which the curved 

 lamellar particles of composition are the most remarkable. 

 The curvature of their surface corresponds to that of reni- 

 form or globular shapes, so that the quantity of its deviation 

 from a mathematical plane depends upon the radius of cur- 

 vature. Commonly they consist of columnar, sometimes of 

 lamellar and granular particles. They occur in octahedral 

 Fluor-haloide ; in prismatic Iron-ore ; in prismatic Hal- 

 baryte, called curved lamellar Heavy-spar ; in rhombohe- 

 dral Quartz, called Calcedony ; in rhombohedral Lime-ha- 

 loide, in rhombohedral Antimony, &c. 



The composition is very often still more complicated ; 

 we may dispense, however, with entering into a greater 

 detail, since the given examples are perfectly sufficient 

 for explaining every other case. 



. 190. CHARACTERISTIC MARKS OF COMPOSITION. 



Imitative shapes, and the want of cleavage, are 

 the chief characters, from the presence of v ich 

 composition may be inferred, if this should not be 

 observable at first sight. 



An individual formed under such circumstances as to 

 be beyond the reach of any foreign influence, will always 

 assume a regular form. 



If, therefore, we meet with minerals which evidently 



