What does mod do?
Heart Crystals Mod 1.7.10 allows you to find and mine heart crystals which generate underground. When you mine one, you can eat it to gain one heart of maximum health!
Heart crystals look like this and generate very rarely under the height of 64 underground.
If you die, your heart crystals are dropped as items along with the other items you drop, so try not to fall in lava.