Despite being one of the most essential minerals on our planet, vital for maintaining human life, how many of us have ever considered where the salt we use every day comes from?

As a documentary photographer and writer, I am used to challenging assignments in far-off places. But as I stood, exhausted from many days of sleep and oxygen deprivation, staring up at the summit of Mount Kilimanjaro, the highest freestanding mountain in the world, I couldn't help but wonder if this would finally be a challenge too far?