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TRANSACTIONS OF THE 



FOURTH ORDER— COAL. 



Metallic or wax lustre. Color black and brown. 

 Mono-axis or amorphous. 

 H. from | to 4. 



G. from 1, 2 to 2, 1. Examples — anthracite and bi- 



tuminous mineral coal, Jam. 

 When G. from 1, 9 to 2, 1 ? no brown color. 

 Examples — rhomboidal graphite. 



APPENDIX FIRST— SLATES. 



From common lustre, in a small degree, to dull. 

 Slaty. 



H. from 1 to 7§. 



G. from 1, 8 to 3, 1. 



The slates may follow after the order Mica. 



APPENDIX SECOND— CLAY. 



From glimmering to dull ; no regular forms. 

 Earthy, uneven, splintery. 



H. from 1 to 6. 



G- from 1, 6 to 3, 4. 



When splintery, H. from 1 to 2 ; G. 3, 2 and 

 more. 



They may follow after the Porodine. 



