12/16/20 8:15 AM | 3 Min Read

What do You Mean by "Representative Sample"?

Posted By
Carl Sorrell
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What do You Mean by

Part 1 - It's All the Same Stuff!

At the IntoCeramics laboratories, we are extremely careful when handling samples we receive for testing in formulations. We are also very particular about how we handle the materials we produce during those tests.

Explaining to our clients why we do this is not always easy. To many of them, their stockpile of material - or minerals in the ground - all look the same.

Here’s how we try to explain it…

Imagine a box of Raisin Bran cereal. If you shake it hard for a long time, where do the raisins go? Eventually, the raisins - being denser and rounder than the flakes - sift themselves all the way to the bottom. (We don’t have anything against raisins - you can also view it as the lighter flakes moving to the top.)

The same is true when Mother Nature deposits or moves materials around over a couple of million years. For example, a sedimentary clay forms when water transports clay particles downstream until they finally settle in a low spot.

These separation phenomena can be loosely defined as particle segregation. The images below, courtesy of ZKG Cement (L) and Processing Magazine (R), shows how particles segregate when a stockpile of similar material is made from a single feed stream of material.

Segregation of bulk solids - ZKG Cement-1Segregation-pile-formation - Processing Magazine

The larger, heavier particles flow down and to the outside of the pile, much like the raisins in the cereal box. Lighter, smaller particles tend to be more concentrated in the center of the pile.

As a result, incorrect sampling of the pile can lead to non-representative samples and misleading test results. If not identified and corrected, this will impact the formulation of your mineral or waste stream into ceramic products.

Any of the following properties can be affected:

  • Particle size analysis
  • Chemistry (especially if it is particle size dependent, which is very common)
  • Mineralogy
  • Drying properties
  • Sintering
  • Physical properties once fired

We have seen many developments and operations fail because of inaccurate sampling that led to incorrect process design.

IntoCeramics will help you avoid these mistakes by making sure proper samples are taken and that we design your process to handle the inherent variations found in your materials.

Of course, if we ever do encounter that rare situation where we find it really is “all the same”, we’ll be the first ones to let you know!

Next time: Part 2 – The Scandalous World of Drill Borings and Reserves Estimation

Topics: Manufacturing, Analysis

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