Hi Dana thanks for writing in. CENO is a Spanish word that means "Frowning" and it sounds like you have being doing a bit of that, trying to figure this mark out.
I think if you carefully examine the mark, using a jewelers loupe or magnifying glass in good light, preferably daylight, you will find the mark is GENO - with a G - not CENO.
The "opals" & "raw diamonds" sound a bit puzzling. These white stones could possibly be moonstones but without seeing an image, hard to say for info on moonstone please click here...
