In the Starship Update at about
21:05 Musk says:
We’ve gone through various iterations of heat shield, there’s a lot of ways to skin a cat here. Ultimately we decided to have a heat shield of hexagonal tiles, ceramic tiles that are basically like a tiny glass vermicelli at a microstructure level; very light but very crack-resistant, essentially glass tiles.
Question: What might the description "tiny glass vermicelli at a microstructure level" refer to? Is it something like a compressed, fused glass wool?