Silkrock
Silkrock is a peculiar mineral found across Venviri. On their own silkrock are nothing more than an ordinary pebble, but when gathered together they form an unbreakable silken bond. While most still drift around as small clumps, some have gathered together to form entire hills and mountains.
The rock's marbled appearance is iconic, with swirling patterns of reds, greys, and blacks. The silk is a pale white and has a smoky odour.
A few unfortunate tortonids will grow such a large plate of rock on their backs that it crushes them. Geological analysis shows crumpled corpses of these animals littered underneath silkrock hills.
Silkback tortonids use silkrocks as a defense mechanism, piling them up on their shell. One of the smallest tortonids, their silken shell extensions can be triple, even quadrupal their true size. This also makes them one of the strongest creatures on the planet, capable of supporting fifty times their body weight on their back.
"unbreakable", hmm? Surely a useful material, if only it could be separated...