No color inside of the matrix, never seen another pelt like it. Yes the outside design resembles a miller type swirl pattern but still not seeing pelt ??
No Christensen, IDK what it is for sure. but you can rule those two out. By a process of elimination you'll get close. I think there were a few different manufacturers that made very similar marbles that's what makes this one somewhat difficult to positively I.D.
Might be excess colorant. Aventurine will sparkle, excess colorant doesn't. Check it with a bright light shinning on it not under or behind it. Looks from here like you may have a mixture of both. Av is sometimes created during a chemical reaction in the glass during manufacturing and sometimes intentionally added.
One of my favorite German Hand Medes. At first I thought the sparkles in the green ribbons were tiny air bubbles. But I gut my loupe out and discovered that not only was it av. but the marble was also a 3 stage, the green and orange ribbons aren't touching the white solid core.