Climbing Chalk and Contaminants
Climbing chalk is “just” Magnesium Carbonate (MgCO3) but because of the way it is produced it can contain “heavy metal” contaminants like Lead and Mercury. Magnesium is actually named after Magnesia, a district in the ancient Greek region of Thessaly, where magnesite deposits were first found. Nowadays most magnesium carbonate comes from mines in China.
Most climbing chalk these days is mined from the earth in large open-pit mines in a process that is both energy intensive and polluting. It’s the mining process that causes traces of contaminants to be present. The process roughly goes like this. First magnesite is extracted from the ground & then purified in a series of acid baths to end up with the final magnesium carbonate product climbers call “climbing chalk”.
If you don’t do the purification right you tend to end up with all kinds of nasties in your chalk: Lead, Arsenic, Mercury, Chromium, Nickel, Zinc, Copper, Barium, Cadmium, Cobalt, Antimony, Selenium, etc … Certification processes have sprung up to define “safe” & “acceptable” levels of contaminants in MgCO3.
After the purification process you end up with Magnesium Carbonate and depending on the level of purity it is then sold as “Pharma Grade”, “Cosmetics-Grade”, “Consumption-Grade” and “Sports-Grade”. Because Magnesium Carbonate is used in all manners of applications besides climbing. It’s so cheap it is often used as a filler, can be made into a food supplement for humans and is used in cosmetics products. Climbers in fact only use a tiny fraction of the Magnesium Carbonate produced worldwide.
But this is not the only way Magnesium Carbonate can be produced. MgCO3 can also be produced by Electrolysis and Thermal reduction. In fact, those processes pre-date the current way of mining it from the Earth’s crust. Mining however, especially in low-labor-cost countries like China, is the cheapest way of producing magnesium carbonate. No wonder then that this has become the way most climbing chalk is made.
Recently more forward-looking climbing brands like Tokyo Powder Industries and ourselves have started to look at moving away from mining by switching to synthesised Magnesium Carbonate. At Chalk Rebels we have chosen a seawater-based synthesis process for our next batches of liquid chalk. While still energy-intensive, it ends ups in a far cleaner product with nearly no contaminants. The cool thing about a seawater-based process is that it effectively turns the toxic byproduct of desalination (brine) into clean drinking water, salt & magnesium carbonate.
While staying within safe levels for human consumption requires significant effort in the mined process, it’s a no-brainer in the synthesised processes. E.g. our newest process allows us to be 400x below the safe threshold for Nickel and 20x for Lead.
These contaminants are in no way going to affect the performance of your chalk but it’s nice to know that your chalk is pure & does not contribute to environmental degradation.
Photo by Vlad Chetan