a glass key

This is a long thin key, the bulk of it made of a single piece of dark glass.
The surface is scratched with small lines and symbols. The stem of the key is
fused with a flat handle of black rock, smooth to the touch.

It is a glass key.
It weighs about one pound.

You identify a glass key.
It is an unsellable key.
It weighs one pound and two ounces, and it is worth about five celeb.
Its keywords are key and glass.