Fulgurites are natural tubes or crusts of glass formed by the fusion of silica (quartz) sand or rock from a lightning strike. By definition, it can be considered petrified or fossilized lightning.
All lightning strikes that hit the ground are capable of forming fulgurites. A temperature of 2,100 degrees kelvin is required to instantaneously melt sand and form a fulgurite, and lightening strikes are known to exceed 30,000° K.
For one tiny moment, this may have been the hottest point on Earth, perhaps even exceeding the temperature of the Earth's core (6,000° K.)