Crystoplast was a clear substance with considerable strength to weight ratio, suitable for structural use even for extended clearspans.
It was sufficiently non-wearing and corrosion resistant in oxygen/water vapor atmospheres to be used for architectural purposes in structures with long intended lifetimes, such as domes covering large public buildings and spaces. Crystoplast was routinely in use elsewhere, but new to Grayson, when Adam Gerrick suggested it be used for towns and farms on the planet Grayson as part of greatly improved protection from the local, somewhat toxic, environment. (HH4)
The material used in some of the domes was three millimeters thick. (HH5)