INSTRUMENTS AND CHKMK'A!. Tl STS 555 



iu;iy lie held at the lip )t" the Mile OOH6 when- it will lie heated 

 hot without actually heating the forceps at all. When sufficiently 

 hot, it will color the flame intensely red. In the teMing of minerals 

 for fusibility a slender fragment, not larger than 1 ram. in thickness 

 at the point, should bo solocted ; if the mineral fuses with difficulty, 

 very fine-pointed pieces should be tested before it is decided that 

 the mineral is infusible. Select a suitable piece of almandite 

 garnet, hold it as in testing for flame coloration, at the tip of the 

 blue cone, care being taken that it projects beyond the forceps. 

 Almandite fuses at 3 ; its edges will become rounded and at the 

 highest temperature the entire end of the fragment will be globular. 

 Select a piece of orthoclase of the standard size (fusibility 5) ; after 

 heating in the same way it will be found that the edges are rounded 

 only; fine needle-like pieces will fuse to a globule on the end. 



Fusibility is determined by comparison with a mineral selected as 

 a standard. The scale of fusibility was arranged by Von Kobell and 

 modified by Penfield. Specimens of the standard minerals should 

 be tested. 



Fusibility 1, Stibnite, large fragments fuse in the yellow gas 

 flame. 



Fusibility 2, Chalcopyrite, small fragments fuse to a globule in 

 the yellow flame. 



Fusibility 3, Almandite, coarse fragments become globular in 

 the O. F. * 



Fusibility 4, Actinolite, coarse edges are rounded in the O. F. 



Fusibility 5, Orthoclase, needle-like fragments become globular 

 in O. F. 



Fusibility 6, Bronzite, needle-like fragments become rounded 

 on the point. 



While heating a mineral for its fusibility, it should be carefully 

 watched and the following noted : whether it intumesces, that is, 

 swells and bubbles when it fuses ; whether it swells or curls with- 

 out fusing exfoliates; whether it becomes enameled or is glassy 

 and clear after fusion ; or whether it fuses to a blebby, vesicular 

 glass. All these conditions are quite important in the determina- 

 tion of minerals. 



Hammer and anvil. Any small hammer will serve, as it is used 

 only to break small pieces of minerals and to flatten malleable 

 buttons. 



A block of hardened steel 3 cm. square serves as an anvil ; both 

 hammer and anvil should be well polished and kept free of rust. 



