554 MINERALOGY 



the hammer while it is still plastic ; or better still, make a fresh 

 bead and dissolve less oxide in it. It is always better to use a very 

 small amount of material at a time and work up to the color by 

 several additions, examining the bead after each addition, than to 

 at once saturate the bead. After an examination of the color pro- 

 duced in the O. F. the same bead is now held in the R. F., so that it is 

 completely covered, on all sides, by the flame, and in this way 

 protected from the oxygen of the air. The manganese sesquioxide, 

 Mn 2 3 , which colored it violet-red in the O. F., will be slowly re- 

 duced to manganese protoxide, MnO, which has no perceptible 

 coloring effect in borax. The bead when cold and completely 

 reduced will be clear and colorless. Highly charged beads may 

 assume a light violet color due to oxidation while cooling. They 

 should be cooled quickly by pressing them while still hot on 

 the anvil with the hammer. This same bead may be again oxi- 

 dized, when it will become violet-red. For practice in handling 

 the flames the student should alternately oxidize and reduce it 

 several times. 



Salt of phosphorus, NaNH 4 HPO 4 . 4 H 2 0, is used in the bead 

 tests in the same way as borax ; the two are known as the glass 

 fluxes. Upon first heating the salt boils violently, due to the large 

 quantity of water it contains ; for this reason the bead must be 

 built up by installments, heating after each addition until boiling 

 ceases and a clear colorless glass remains. During the fusion the 

 composition has been changed by the loss of water and ammonia ; 

 sodium, metaphosphate remains, NaPOs; this is the S. Ph. bead. 

 Its use is the same as the borax bead. 



Platinum forceps are used to hold fragments of minerals in the 

 O. F. either to test their fusibility or for a flame coloration. The 

 most convenient model, Fig. 531, is made of steel nickel plated ; one 

 end is the ordinary steel forceps used in picking up hot beads, etc. ; 



the other end is self- 

 holding and platinum- 

 tipped. Minerals with 

 FIG. 531. luster which fuse 



easily, or those which 



reduce to metal, should not be held in the platinum, as they will 

 alloy with it and the forceps will be ruined. 



Illustration. Heat a slender fragment of strontionite (SrCOs) 

 in a small well-pointed O. F., holding the fragment of mineral in 

 such a manner that it projects out beyond the platinum tips and 





