 Pressing extremely firmly will cause a catastrophic breakdown in the sparse structure, causing it to shatter like glass (a property known as "friability"), although more modern variations do not suffer from this.Despite the fact that it is prone to shattering, it is very strong structurally.Its impressive load-bearing abilities are due to the dendritic microstructure, in which spherical particles of average size 2–5 nm are fused together into clusters.