I doubt that the black is opaque.
Get a strong pen-light underneath it and look again.
I am guessing that it looks purple.(maybe brown)
The white is opalescent imho and many marble companies use "cullet glass" or leftover glass from the factory that mad "Ponds Cold Cream" Jars.
This one is not a Peltier.
It is a WVS or West Virginia Swirl that includes many companies.
My guess ( I suck at WVS ID) would be Alley Agate.
I appreciate the nice images, the size and you patience here.
Marble--On!!