56 



MINERALS AND GEOLOGY 



As the substance possesses a metallic aspect or lustre, he tin 

 bracket 2. There he finds : 



2 ( Occurring in detached grains or scales ...................... 3 



| Occurring under conditions .............................. 6 



As the specimen is not in the form of loose grains or scales, but in 

 that of a solid mass, he turns to bracket 6, which reads : 



P ( Hardness sufficient to scratch glass ...................... , . 7 



"j Hardness insufficient to scratch glass ...................... 15 



As the mineral is not hard enough to scratch glass, bracket 15- 

 must be, referred to, which reads : 



, - j More or less distinctly malleable .......................... 46 



Lo } Not malleable .......................................... 20 



As the substance is not malleable a small piece breaking readily 

 into powder under the hammer tbe inquirer turns to bracket 20, 

 He there finds : 



( Structure distinctly scaly or micaceous, the substance admit- 

 20 ) ting of separation into thin leaves, plates, or scales ........ 21 



' 



Structure not micaceous or scaly. . 



As the mineral under investigation does not present a scaly 

 micaceous structure, and does not soil the hands or leave a mark on 

 paper, reference is made to bracket 23. This reads : 



( Affecting the magnetic needle ; colour, browish-yellow 



23^ MAGNETIC PYRITES (No. 19.) 

 ( Not magnetic 24 



A small particle or two being chipped off the specimen, and tried 

 by a common magnet or the entire specimen being held near a 

 magnetic needle attraction is found to ensue ; hence the substance 

 is shewn to be Magnetic Pyrites, No. 19 of the classified series de- 

 scribed in the following pages. By reference to the description there 

 given, the various physical and chemical characters of the substance, 

 its percentage composition, localities, etc. , may at once be ascertained. 

 In using the Key, caie must be taken to pass regularly from one 

 indicated bracket to the other, without attempting, on account of 

 foregone conclusions respecting the nature of the substance, to jump 

 over any of them, or to refer to others than those actually indicated. 

 If this be not attended to, errors and confusion may easily arise. 



As the above Key contains a good many minerals of rare or com- 

 paratively exceptional occurrence, the beginner may frequently avoid 

 unnecessary trouble, in making out the name of an unknown sub- 





