Four primary types of potash ore are commonly extracted by miners: polyhalite, langbeinite, sylvinite and carnallite. Sylvinite and carnallite are the most abundant sources of potash, but it’s been said that carnallite is the less desirable of the two.
Part of the reason carnallite tends to find less favor with potash miners is that it cannot be mined using conventional techniques — it is simply too soluble to be mined in a stable way. What’s more, processing carnallite can require more energy than processing sylvinite.
Despite those challenges, carnallite does come with a few niche benefits. Read on to learn more about what they are, and why it can still be valuable to mine carnallite.
The sylvinite process
As mentioned, carnallite is generally harder to mine and process than sylvinite. For that reason, it’s useful to consider sylvinite mining and processing when looking at the value and drawbacks of carnallite.
Sylvinite is made up of the salts potassium chloride and sodium chloride, and has been mined and processed in abundance by major potash companies like Potash Corporation of Saskatchewan (TSX:POT) and Mosaic (NYSE:MOS). The process typically looks like this:
- Dig: Potash ore is dug out and brought to the surface via a shaft.
- Crush: The ore is crushed, ground and de-slimed.
- Float: A flotation process separates potash from a salt mixture.
- Spin: Centrifuges separate potash particles from brine.
- Crystalize: Potash concentrate is sized, compacted and crystallized.
Those steps are not simple, but are well understood and can easily be used to process sylvinite ore. Many companies prefer sylvinite to carnallite for this reason.
The carnallite process
Unlike sylvinite, carnallite can’t be mined and processed using conventional methods. Solution mining has to be used instead.
Solution mining consists of drilling holes into an ore body and pumping heated water into the deposit. The heated water dissolves carnallite and brine, allowing them to be pumped out through the holes. The pumped solution goes through an evaporation process that removes water and magnesium chloride and leaves behind potassium chloride and sodium chloride.
Because salts go in and out of solution at different temperatures, the potassium chloride and sodium chloride are put into crystallizers where they’re heated at different temperatures to separate the salts. From there, they are processed into their final products, much like in conventional mining.
As for magnesium, because it is the last mineral to leave water, it is removed early in the process and treated separately.
Why do people still mine carnallite?
It is true that sylvinite is easier to mine and process than carnallite, but miners still extract carnallite simply because it is available. It can be found in deposits that are vastly distributed across the globe in places like the US, Canada, Russia, Germany and parts of the Middle East.
Magnesium is considered a contaminant when processing carnallite, but it can also be seen as an additional commodity. Magnesium is used in everything from personal health supplements to complex alloys for planes. That can make carnallite a great opportunity for miners that want to diversify their market and sell magnesium as a commodity.
In some cases, effective solution mining can be cheaper and faster than conventional mining. It also comes with reduced engineering and safety risks since less digging is required and workers don’t have to enter underground spaces. Solution mining isn’t an exclusive benefit to carnallite, but the process comes with a lot of upside for miners if done properly.
The process is less environmentally invasive as well, requiring less digging and overall space to conduct operations. The caveat here is that solution mining will require higher water inputs than conventional mining.
The bottom line
Sylvinite makes up the majority of the potash market and is great for miners specializing in potash — but carnallite still holds value when solution mining processes are used well. Magnesium, its main by-product, is also a benefit.
This is an updated version of an article originally published by the Investing News Network in 2013.
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Securities Disclosure: I, Sivansh Padhy, hold no direct investment interest in any company mentioned in this article.