You approach cautiously. Surely nothing this valuable would be left here, unattended and unprotected.
You circle it twice, looking for any sign, any hint of a shadow of trouble.
No strings, no trigger plates...
Swift as lightning, your hand passes through the shaft of light, reaching to the ceiling.
For a breif moment, the aerial ballet of the dust particles is halted, but nothing else happens.
You try again, holding your hand there a fraction of a second longer... nothing.
Eventually, you try peeking downward at the gem. A half of a glance and nothing happens.
You look longer. The beam of light shines up at you, but you don't notice anything particular about it.
Eventually, you figure that you have to look into it like a telescope.