Canada is one of the top graphite-producing countries in the world with over 40,000 metric tons of the mineral produced in 2018. Interest in graphite has been growing recently due to Tesla’s announcement that they will be sourcing ingredients for their batteries (like lithium, cobalt, and graphite) from North America. Canada is strategically positioned for this new venture, as high-quality graphite deposits have been discovered across Ontario, Quebec, and Newfoundland. For companies looking to capitalize on this opportunity, accurate metallurgical testing of graphite samples is required to determine which processing method yields the highest grade and quality of the mineral. Here’s a quick rundown of how we perform these tests at Sepro Labs.

Your Simple Step-by-Step Guide To Graphite Testing

There are a few different ways to perform metallurgical testing for graphite depending on what you’re looking to achieve. We can provide tests that involve flotation, gravity concentration, leaching, scrubber testing, flake size characterization, and assaying for graphite. The sample requirements vary depending on which testing procedure is performed.

It’s essential to understand both the purity and flake size of your graphite deposit, as both of these factors determine the value of your graphite. Large and coarse graphite flakes have hundreds of applications and are therefore more valuable. While graphite is being used in modern day electric vehicles, its main use is still in refractories where larger flakes mean less impurities. A larger flake size also allows graphite to resist the extremely high temperatures used for steel and metal fabrication.


Graphite under a microscope. Large graphite flakes are more valuable than finer sizes.

Graphite Assays

At Sepro Labs, we perform a multi-stage process for graphite assaying which involves the removal of the carbon associated with other minerals and all potentially volatile compounds in order to avoid the bias that straight carbon analysis would otherwise include. After removal of these compounds, the graphite is measured by thermal decomposition and gravimetric determination.

Obtaining a representative sample in the assay aliquot is a common challenge due to graphite’s drastically different density, shape, and electrical conductivity. To support our graphite metallurgical test programs, Sepro Labs performs graphite analysis on large aliquots ranging from 5 to 10 g which are 10 to 20 times larger than the aliquots used by typical exploration assay procedures.

Flake Size Characterization

Remember, the larger the flakes, the more valuable the graphite. The key for this procedure is to quickly identify the flake size of the easy to recovery graphite as well as to understand the challenges of recovering and upgrading the remaining graphite. Our goal is to do this in a cost-effective way.

  1. A sample of approximately 10kg is crushed and ground to a coarse size (0.8–1.0mm).
  2. Our MAT super-panner is used for gravity separation of the crushed material. Froth flotation can also be used at this stage.
  3. The graphite concentrate is then sieved for accurate flake sizing.

Froth flotation can be used for flake size characterization of graphite.

This test gives us a clear indication of the size distribution and liberation of the graphite, along with revealing which factor(s) would have a direct effect on the recovery and purity of the graphite concentrate.

Graphite Test Results

Based on the results of the assay and flake size characterization, you will be able to see how the recovery process will affect your graphite project economics. If the results show promise, we will continue with testing to discover the optimal way to recover the graphite. 
Sepro Labs has performed metallurgical tests for graphite projects situated in the graphite-rich provinces of Quebec and Ontario as well as in various regions of Africa. To learn if your next graphite project should get the green light, contact us today and we’ll help you make accurate, data-driven decisions.