This is a beautiful handmade marble that was made in the style of the old Christensen Guinea marbles that were made for the playgrounds. This one is far more interesting of course though, since it has goldstone and green aventurine included for just the right amount of sparkle over a dark cobalt base. That cobalt glass is stunning when you back light it, giving you a deep purple transparent hue, while it looks black in hand regularly. Sweet little gem, wish I knew who made it!