Rods or Balls

Rods or Balls

Mill operators will not get to design too many mills, but this doesn’t mean that the information that has been compiled isn’t of interest to the operator. Knowing the ore body shape, size, and content will give the operator prior knowledge of operating conditions to be expected.
It is also beneficial to know how this information is obtained. The clearer the operator sees the problems the easier it is for him or her to react to his or her circuit. With this in mind I will explain how this type of information is discovered.

When designing a mill you must answer a list of questions:

  1. How many tons are there to process?
  2. How hard is the ore?
  3. How much does it have to be ground before it is possible to separate the mineral from the rock?

By compiling the answers to these questions it is possible to come up with the size and type of mill that is required to treat any particular ore body. The type of the mill is identified by the kind and shape of the grinding material inside of the mill. This material is known as the grinding media.

Steel Rods & Steel Balls


The first question to be answered is the TYPE, SIZE and VALUE of the ore body. In the life of any mine this will be one of the very first things learned. The answer will be determined during the exploration stage by a diamond drill survey. This type of drill, as you know, drills down hundreds of feet and brings up what is known as core samples. These core samples are assayed. With careful documentation as to where it was taken and the depth that it was taken from, it is possible to develop an accurate idea of the ore body characteristics. This survey gives the TONNAGE, the SHAPE, the CONTENT, and the VALUE of the ore body. This information can be used by the operator to determine expected operating conditions by simply asking the mining department which area of the ore body the mill feed is coming from.