Zaterl emerald
A Zaterl emerald was a semi-mythical gemstone reported to be housed in the ruins of Ligillium.

In 2367, Captain Jean-Luc Picard offered to take  there to convince her to accept arbitration in the matter of the Contract of Ardra. She mentioned the Zaterl emerald and asked Picard if he really knew where it was, which he confirmed. She congratulated him for his cleverness, but said she had enough jewels and wished to choose her own prize – Picard himself.  ()
Gemstones