Tholian crystal-lattices were intricate crystalline objects created by the Tholian race. Such objects were apparently common in Tholian culture, but their significance and purpose were unknown in the Federation.
In the 2360s and 2370s, a number of crystal-lattices were discovered at the archaeological dig on Drura Sextus. These were uncommon in that they bore markings believed to represent an unknown Tholian written language, and in that they were capable of creating sound and colors when touched. (CoE eBook: Ghost)