Glass is an amorphous solid, lacking the lattice patterning which characterizes crystals. Despite being brittle and lacking coherent molecular ordering, glass can possess surprising strength and rigidity. Besides the ostensible molecular chaos, this durability is further unexpected because amorphous systems also suffer from large anharmonic fluctuations.
The secret of’ glass’ strength is an internal network of force-bearing particles spanning the substance. This branching network acts like a skeleton that prevents glass from yielding to stress, even though the skeleton makes up only a scant fraction of the total material. The orderly skeleton of glass dynamically emerges in an act of self-organization as glass gradually cools into its destined shape. Rapid cooling prevents the strength skeleton from forming.
Glass is ~70% silica. Earth’s crust is 59% silica, which is the main constituent of almost all rocks. Besides glass, silica heavily figures in cement and mortar.
References:
Hua Tong et al, “Emergent solidity of amorphous materials as a consequence of mechanical self-organisation,” Nature Communications (25 September 2020).
“A clearer view of what makes glass rigid,” ScienceDaily (25 September 2020).