Fighting the cold? Need help cooking? Don’t underestimate the power of hot rocks! Stones can hold a lot of heat, and radiate that warmth for a long time when properly insulated. Start with rocks from a high, dry area. Never use rocks from a wet area. They may have trapped moisture which can cause them to explode when heated. Avoid glasslike or crystal filled stones. Don’t use slate or shale, either. These are prone to explosion and breakage near heat. Just grab some plain old ugly rocks from a high dry location, heat them up and enjoy the results.
Source: http://www.outdoorlife.com/5-ways-to-use-hot-rocks-in-survival-situation
1. Bed Warmer
For a warm and comfortable night, heat large flat stone to about the same temperature as scalding hot tap water. Wrap it in tough cloth or clothing, and put it in your bed or sleeping bag. The heat will soak into your cold bedding and you’ll drift off to a snug night of slumber. I’ve had rocks remain warm as long as seven hours this way.2. Rock Boiling
Rock boiling can be used to prepare soups and teas, and boil your water to disinfect it. Collect about two dozen egg sized or slightly smaller stones to rock boil 2 to 4 quarts of water. Heat them in your fire for 30-45 minutes. Use sticks or split wood tongs to pick up the rocks and drop them into your water. Use one or two at a time, and rotate “cool” ones out and hot ones in.3. Rock Frying
For small cooking tasks, chuck a flat rock into the fire for ten minutes to heat it up. Once hot, slide it out of the fire with a stick and dust off the ashes. Drip a little oil on the stone and set your food on the rock to cook. This is a dead simple way to make delicious fried foods, and you don’t even need a frying pan! And for a more permanent set-up, place a large slab of stone over a trench or on top of stone legs. Build a fire underneath, heat the stone, drop your food on top and listen to your meal sizzle!4. Heat On Injury
For sprains, strains, cramps and other maladies, a warm rock can provide soothing comfort when held against the affected area. Warm stones can even help with problems that are severe, like hypothermia (cold exposure that can lead to shock and death). To treat this with hot rocks, place a warm stone under each armpit and between the thighs of the exposure victim. Wrap them up and repeat the treatment until their body temperature rises.5. Punch Holes in Ice
Want some fresh fish, but you lack the tools to bore a hole through the ice? Step back a few thousand years and use something our remote ancestors would have used – a hot rock. Simply burn a large fire on the shore, heat up a large stone in the blaze. After an hour of heating, use a shovel to carry the dangerously hot stone to your ice fishing spot and set it on the ice. It will begin to melt the ice immediately and work its way downward. Soon the rock will melt through the ice and drop into the dark water below. Your ice fishing hole will be open, smooth and ready to fish.Source: http://www.outdoorlife.com/5-ways-to-use-hot-rocks-in-survival-situation