117] Sampling of Minerals 83 



are those of mineral phosphates and limestones. Much ingenuity 

 has been expended in devising machinery and implements with 

 which an accurate sample can be drawn. The simplest of 

 these is the sampling spade, shown in fig. 35. When this is 

 driven into a mass of ore a certain small 

 quantity is collected in the central com- 

 partment, whilst a much larger portion 

 finds its place on the sides. A dex- 

 terous throw with the shovel sends all 

 the larger portion off on to another heap, 

 leaving the small part still in its place. This is then thrown 

 on to another spot. Thus, after digging away a large portion 

 from different parts of the bulk we get a large and a small 

 heap, the small one being a fair sample of all the rest. By 

 repeating the operation on this sample a still smaller sample 

 is obtained. 



When, by repeated samplings of this kind, a sufficiently 

 small heap has been formed, it is spread out on the ground, 

 the larger lumps broken up, and half-a-dozen small spadefuls 

 taken from different parts. This small quantity is broken up 

 to pieces about the size of marbles, spread out, and five or 

 six handfuls taken from different parts. This portion may be 

 sent to the laboratory. 



Should a sampling shovel not be available, the first heap 

 may be made by selecting a spadeful at a time from different 

 parts of the bulk, and reducing this to smaller heaps as before. 



117. In a sampling machine the whole mass of the mineral 

 is made to pass through a spout which is continually moving 

 backwards and forwards so as to distribute the ore all over a 

 large platform. At one part of the platform is a hole, so that 

 whenever the spout passes that place a small portion of the 

 mineral falls through into a receptacle beneath. This portion 

 is again passed through the machine, until it becomes of 



g 2 



