Freezing
The mineral is water, or rather snow. Your adventurer is in the mountains. He can preserve his meat by climbing into the colder regions and burying it in snow. He could build up a considerable cache in this way.
People who have died climbing Everest are still to be seen, their bodies perfectly preserved in snow and ice. Also of course there have been finds of much older bodies being preserved in the snow.
THE MUMMY OF an ancient Inca girl sits literally frozen in sleep at a museum in Argentina.
The mummy, called La Doncella or The Maiden, is that of a teenage girl who died more than 500 years ago in a ritual sacrifice in the Andes Mountains.