Keva

Kevas were commonly traded items in the 23rd and 24th centuries, usually in tandem with trillium.

Spock presented himself as a trader of kevas and trillium while undercover on Organia in 2267. Arne Darvin also claimed to have traded in kevas and trillium in the 2370s, prior to his capture by the Cardassians. 

Kevas had a distinctive scent when burnt, and was used in incense on Vulcan. Amanda Grayson was fond of the scent of kevas and trillium, and Spock was reminded of her when he encountered the same scent at the Vulcan Embassy on Earth. 

A necklace of kevas was one of the symbols of office for Me'Grmat XIX, Emperor of the al'Hmatti.