The Eye of Gaar was a sacred gem located in the Temple of Gaar on the planet Ventros Prime.
The gem was composed of ammonia and methane ice. When it was brought off planet, it was kept in a casing to keep it in solid form.
The Eye was stolen by a Ventrosian who ended up on Earth. He was followed by two Ventrosian priests who hoped to recover the Eye. After all three were killed, the gem was stolen by the human thief Len Skeggs. He broke the gem out of its casing, and the heat from his hand caused it to turn to gas, killing him. (PROSE: Hot Ice)