Item:Black gold necklace dangling a knotted ball of vines

black gold necklace dangling a knotted ball of vines
Look:	Carved out of additional strands of black gold, the thick vines twist and turn over each other to create a chaotic mass that has no beginning or end. A pair of prongs rests at the center of the ball, perfectly spaced apart to hold a single gem. An empty gem setting mars the necklace's appearance slightly.
Weight:	Unknown
Metal:	Unknown
Appraised Cost:	Unknown
Properties:	This item is worn in the neck slot. This item has more than normal or unusual verbs.
Dimensions:	? length x ? width x ? height
Sources:	Source is Droughtman's Challenge 450/Incidental loot, Droughtman's Challenge 444/Incidental loot, Droughtman's Challenge 441/Incidental loot, Droughtman's Challenge 437/Incidental loot, Droughtman's Challenge 433/Incidental loot, Droughtman's Challenge 430/Incidental loot

The necklace appears to be capable of holding a single gem.
You think that to put a gem into the socket, you need to PUT the gem in the necklace.
You also think that in order to get a gem back out, you can GET the gem FROM the necklace again while holding it.
You think you can also RUB, TAP, TOUCH and CLEAN the necklace.
The necklace seems to be missing a gem.