Master seems a good guess then.
Anyone remember aventurine in moss agate greens?
Oh yes, FWIW, it's a "moss agate" with lower case letters even if it's a Master marble. Master used that term to describe their marbles. The official style name if it's a Master is "Meteor", but it is still a moss agate, little m, little a.
And Akro used Moss Agate with the capital letters.
LOL ... if you already knew that, just pat me on the head and tell me good girl.