16 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



Thus if any mineral above be used in the form of a sharp 

 point it will scratch the preceding members of the series, 

 e.g., should we find a piece of mineral which will scratch 

 calcite but not fluorite its hardness is between 3 and 4, 

 say about 3^2- 



Table VII. — Hardness of Some Common Minerals 



Mineral 



Hardness 



Asphalt 



Augite 



Barites 



Bournonite 



Brown haematite 



Calamine 



Cassiterite 



Cerussite 



Chromite 



Copper glance. . . 



Corundum 



Felspars 



Graphite 



Gypsum 



Haematite 



Hornblende 



Ilmenite 



Magnetite 



Malachite 



Micas 



Mispickel 



Native copper. . . 



Ozokerite 



Pyrolusite 



Quartz 



Salt 



Silver glance .... 



Soda niter 



Spathic ore 



Stibnite 



Sulphur 



Tourmaline 



Wolfram 



Zinc blende 



Coals : 



Anthracite .... 



Bituminous. . . 



Lignite 



1.5 



5.5 



2.5 



2.25 



4.25 



5 



6.5 



3.25 



5.5 



2.25 



9 



6.5 



1.5 



1.25 



5.5 



5.5 



5.5 



5.5 



3.25 



2.5 



5.5 



2.25 



0.75 



2.5 



7 



2.5 



2.25 



1.25 



3.5 



2 



1.55 



7.25 



5.25 



3.25 



2.25 



1.25 



.5 



Remarks on cores 



Melts at about 100°C. 



Brittle 

 Lenticular fracture 



Sometimes magnetic 



Splits easily 

 Cleaves readily 



Sometimes magnetic 

 Very magnetic 



Cleaves easily 



Melts at about 60°C. 



Cleaveless 

 Dissolves in water 

 Breaks in slices 

 Dissolves in water 

 Nodular 



Sometimes flaky 

 Brittle 

 Fractures easily 



Brittle, shelly fracture 

 Brittle, cubic fracture 

 Friable and platy 



