What makes it chrome? Marble ID.

[Bax]

I have several of these, all appear chrome until you hit them with a flashlight. Blue, red, green, pink, orange.. sorry for the not so good photos, but these are hard to get a good shot of because they reflect everything.

[Peltier Mibber]

Here's what I found:

However Alan may know more:

What is iridescent glass made of?

Iridescent glass, sometimes called iris glass, is made by adding metallic compounds to the glass or by spraying the surface with stannous chloride or lead chloride and reheating it in a reducing atmosphere. Ancient glasses appear iridescent from the reflection of light off of many layers of weathering.

Colored Glass Chemistry: How Does It Work?

www.thoughtco.com/the-chemistry-of-colored-glass-6…

[Fire1981]

Don’t ever put them in a fish tank. 

[ann]

This looks like the sprayed type. I know Vacor made some, and a few other companies experimented with iridescence, but not sure they ever produced any in large numbers.

And no, don`t put them in a fish tank!

[Chad G.]

Vacor oily, but not sure ?? that's just what we always called them. Agree w/  Mibber & Ann on the sprayed aspect.

[wvrons]

We made a lot of them at Jabo. I did the spraying on a few thousand.