I was going through a big bag of cats eye marbles and I noticed this one with a sparkly vane in it. It measure .61 inches. Most of the sparkles are dark but there are some lighter gold sparkles as seen in the pictures. Thanks for looking!
That's aventurine. Different from lutz. It's not as valuabe as lutz, but definitely can add value to a marble. Most commonly found with blue/green colors.
I think the gold you're seeing is just the way the light reflects. To tell the difference, lutz will be gold colored even if the light isn't shining on it. Aventurine is dark colored usually until light shines on it.