280 TERMINOLOGY. . 196. 



1, Splendent, 



2, SJtlnlng, 



3, Glistening, 



4, Glimmering, 



5, Dull. 



Splendent faces, or those which possess the highest degree 

 of lustre in the whole mineral kingdom, produce distinct 

 and well defined images of the objects, provided they pos- 

 sess the required extension and evenness. Such faces are 

 contained in many varieties of dodecahedral Garnet-blende, 

 of rhombohedral Iron-ore, of rhombohedral Quartz, and 

 other species. 



Shining is a less degree of lustre ; it is still lively, but 

 does not produce a distinct image. This degree is very 

 common in several species of the orders Spar, Haloide, 

 Baryte, &c. 



Glistening reflects light still more disorderly ; but al- 

 though it does not any longer produce an image, yet it 

 reflects it in pretty well defined patches. This degree of 

 lustre is found in most of those compound minerals, in 

 which the particles of composition are still observable, or 

 at least in which they have not yet entirely disappeared. 

 Examples are pyramidal Copper-pyrites, tetrahedral Cop- 

 per-glance, &c. 



Glimmering does not reflect defined patches" of light, but 

 a mass of undefined light seems spread over the glimmer- 

 ing surface. This degree of lustre is peculiar to the very 

 thin columnar composition (commonly called fibrous frac- 

 ture), and to several other compound minerals, in which 

 the composition disappears, as in the varieties of rhombo- 

 hedral Quartz, called flint, calcedony, hornstone, in com- 

 pact hexahedral Lead-glance, and other minerals. Com- 

 monly this degree is a sign of a compound mineral, the 

 individuals of which are so very small, as nearly to disap- 

 pear. It is produced by the reflection of light from every 

 one of the impalpable component particles. 



Dull possesses no lustre at all. This perfect absence 

 of lustre is almost entirely confined to decomposed mine- 



