Aerogel

The worlds lightest solid material! Aerogel is essentially glass foam. Made from silica and air Aerogel is a material used in aerospace industry where a thermo barrier or insulation is required for extreme temperature differences. Like in a rocket where sensitive electronics need to be protected from thermal damage. It was also used in a satellite that flew through the tail of a comet and returned a sample to the earth for analysis. The Aerogel acted as a"hand" grabbing particles and holding them to be returned to earth. The picture bellow is from this mission. Cutting edge materiality. To give you a sense of price I have a small square that is only 2 cm squared and it is probably worth 60 bucks!

This is the matrix it was packed in.

This is a comet particle embedded in Aerogel

As you can see these crayons wont melt!