Tholian silk is a rare material made by the Tholians.
Tholian silk was highly prized in the Ferengi Alliance, which was largely purchased with Ferengi exports to Tholis of Ferengi bog moss. (DS9 reference: Legends of the Ferengi) Gaila owned a suit made out of Tholian silk in 2376. (DS9 - Gateways novel: Demons of Air and Darkness)
In 2298, the Tholian ambassador Kasrene was impressed that Ambassador Aidan Burgess wore a gown made from Tholian silk. Kasrene considered it an honour. The material, derived from Tholian excretions, was also used by the Tholians themselves to make environmental suits. (ST - The Lost Era novel: The Sundered)
In 2372, Benjamin Sisko was able to obtain a scarf made from the silk from a Tholian ambassador who owed him a favor. He later gave it to Kasidy Yates as a gift. (DS9 episode: "The Way of the Warrior")