231 



MINEKALOGY. 



[Sect. VIIL 



\ 



Sect. 



1 



1 



-"^ 



lime). 5. Pliospiiate of lime. 6. Lamellar felspar. 7. ijock 

 crystal. 8. Topaz. 9- Euby or Sapphire. 10. Diamond. 



S. Toiighness.—This character consists in the resistance ^hich a 

 substance offers to be broken or torn. A soft mineral may be very 

 tough, such as sulphate of lime; a hard one readily fractured, as 

 flint ; and some are both hard and tough, as jade. 



9. The ScratcL—Tv'mls for hardness give a scratch and poAvder, which 

 are useful in the determination of minerals. Thus the ores of iron 

 named hematites, gi^re a red or yellow ochre powder, which at once dis' 

 tinguishes this mineral from the concretionary ores of manganese, the 

 powder of which is black. 



10. The Stahu— This character is only applicable to a few minerals, 

 and those soft. It consists in marking paper or linen with the mineral--^ 

 chalk and plumbago thus leave marks. Plumbago may be thus dis- 

 tinguished from sulphuret of molybdenum, Tvhich it otherwise much 

 resembles, 



11. Unctuosity,—Many minerals are soft and soapy to the touch, suci 

 as talc and serpentine, magnesian minerals. 



1 2. Flexibility, —SeYeral are flexible, such as native silver and copper. 

 Some are both flexible and elastic, as mica. 



13. Df/c^?7%'.— Principally applicable to native metals. Though 

 sulphuret of silver and halloysne cannot be lengthened under the 

 hammer, they are nevertheless termed ductile by the mineralogist. 



14. Tasce.— Only applicable to certain substances, distinguished as 

 bitter, sweet, salt, &c. 



15. Adhesion to the tongue .—GeneYBlly sufficient for distinguishing 

 argillaceous from pure limestones, 



16. Odour. Such as of the bitumens and other similar substances, or 

 by means of breathing on or rubbing a mineral, ^hen a peculiar smell 

 is perceived. 



17. Coid,~The feeling of cold when a mineral is placed in' the 

 In this manner rock crystals and gems can be distinguished 



rom glass and enamel, which otherwise may be made closely to imitate 

 them. 



18. Sound.—Thm property must be taken in its ordinary acceptation, 



and not with regard to the motion given to the molecules by percussion. 



Some substances are very sonorous ; phonclite is so named from this 

 property. 



^ 19. Weight,~This property also to be taken in its common accepta- 

 tion, the mineral being only supposed to be weighed roughly in the 

 hand. In this manner carbonate of lime, sulphate of baryta, and car- 



hand. 



4^ 



bonate of lead may be easily distinguished. 





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 bedc 



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 befe. 

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 stopp 



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 soth'^ 



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