Over 10 weight: 25.8 carats. Size: 34 x 17 x 6.5 mm. Koroit Matrix Opal. You can see here the range of matrix colors from brown/ochre on the left to black hemetite on the right.This is my favorite sort of pattern, with the black lines bordering the sections of opal. Sort of like a stained glass window. The other side has a nice pattern too, but no opal.