Trassy

Part of speech: adjective

Definitions

1. Containing or resembling trass, the porous volcanic rock ground up and used in hydraulic mortar and cement
2. Made of or having the qualities of trass, a crumbly volcanic tuff valued in building for its binding properties
3. Relating to or full of trass, a pozzolanic volcanic material that hardens into strong mortar when mixed with lime

Etymology: "Trassy" is an adjective describing something that contains or resembles trass, a volcanic material. Trass is a pale, porous rock formed from volcanic ash that has been altered and cemented, and it is quarried in the Eifel region of Germany and in parts of the Netherlands and Italy. The term came into English through Dutch or German trade and building language, where "tras" or "Trass" named the stone used in mortar and waterproof plaster. Because trass reacts with lime to set hard even under water, it was prized for building harbours, cisterns, and canal works. Adding "-y" to a noun to mean "having the qualities of" is a common English pattern, so "trassy" simply describes material rich in trass or with its texture and properties. Its use is almost entirely technical, appearing in geology, construction, and historical building descriptions.