18 GENERAL CHARACTERISTICS OF MINERALS. 



high finish of these gems of nature's workmanship. The 

 mineral quartz sometimes occurs in crystals consisting of two 

 pyramids united by a short six-sided prism, and they have 

 generally the transparency and almost the brilliancy of the 

 diamond, whose name they bear in common language. The 

 " diamonds" of central New York, and many other localities, 

 are of this kind. In other cases a large surface of rock 

 sparkles with a splendid grouping of the pyramidal glassy 

 crystals. We might draw other illustrations from almost all 

 che mineral species. But this will suffice to show that in ad- 

 dition to the physical characters above mentioned, there are 

 others dependent on structure, which afford distinctions of 

 species, apparent both in external form and internal cleav- 

 age. 



Still other characters are derived from subjecting species 

 to the action of heat, and to acids or other re-agents. One 

 mineral, when heated, melts ; another is infusible, or fuses 

 only on the edges ; another evaporates. By such trials, and 

 others hereafter to be described, we study minerals in a dif- 

 ferent way, and ascertain their chemical characters. This 

 mode of investigation more minutely pursued, leads to a 

 knowledge of the constitution of minerals, a branch of study 

 which belongs properly to Analytical Chemistry : the results 

 are of the highest importance to the mineralogist. 



It is perceived, therefore, that the learner may (1) exam- 

 ine into the peculiarities of structure among minerals ; (2) 

 he may attend to the physical characters depending on light, 

 hardness, and gravity ; (3) he may acquaint himself with 

 the effects of heat and chemical re-agents — the chemical char, 

 acters. These are three sources of distinctions giving mu- 

 tual aid, and a knowledge of all is necessary to the miner- 

 alogist. To learn to distinguish minerals by their color, 

 weight, and luster, is so far very well : but the accomplishment 

 is of a low degree of merit, and when most perfect, makes but 

 a poor mineralogist. But when the science is viewed in the 

 light of Chemistry and Crystallography, it becomes a branch 

 of knowledge, perfect in itself, and surprisingly beautiful in 

 its exhibitions of truth. We are no longer dealing with 

 pebbles of pretty shapes and tints, but with objects modeled 

 by a Divine hand; and every additional fact becomes to the 

 nind a new revelation of His wisdom. 



Mention examples. What other characters are there ? Enumerate 

 the kinds of characters presented by minerals. 



