THE PROSPECTOR'S HANDBOOK. 



SCALE. 



1. Talc (such as soapstone), easily scratched by the 

 finger nail. 



2. Eock salt (also gypsum, zinc, &c.), not easily scratched 

 by the nail, nor can scratch a copper coin. 



3. Calc spar (transparent), both scratches and can be 

 scratched by a copper coin. 



4. Fluor spar, not scratched by a copper coin and does 

 not scratch glass. 



5. Apatite, with difficulty scratches glass and is easily 

 scratched by a knife. 



6. Felspar, scratches glass and is not easily scratched \>y 

 a knife. 



7. Quartz, not scratched by a knife and easily scratches 

 glass. 



8. Topaz, harder than flint. 



9. Corundum, oriental emerald, sapphire, &c. 

 10. Diamond, scratches any substance. 



The hardness of minerals that can be scratched by the 

 finger nail is 2 or less, and by a copper coin less than 4. 



Minerals may often be recognised, or their nature verified, 

 by the crystallization they assume. 



The following are the fundamental forms of crystals : 



1. Eegular system (called the cubic, octahedral, &c.). 

 In this system there are three equal axes- (imaginary) pass- 

 ing through the same point and at right angles to each 

 other. 



For examples 



COBE. 



OCTAHEDRON. 



TETRAHEDRON*. 



RHOMBIC 

 DODECAHEDRON* 



Fm. 24. 



FIG. 25. 



FIG. 27. 



2. Square prismatic system (has three axes at right angles 

 to one another of which two are of equal length). 



