Raven Sky = Sardonyx

Raven Sky - totally looks like Sardonyx.


These are a black base, roughly encased with Raven Sky, some with a trail of white, and mashed.

For comparison - here's what the real deal looks like. Less blue, but the shading of the banding is a nice match. 

As to why I'd want to imitate a fairly inexpensive stone with my expensive time ... ? Because it's cool, that's why.