What type of markings represent a diamond on jewelry

The markings are typically for the type of metal or manufacturer an not the stone, unless it says cz then it is indicating that you do not have a diamond but rather a cubic zirconium. In rare instances the stones carat weight may be listed either ct meaning carat weight for one stone, or tw for total weight of more than 1 stone. If you tell me what the marking says, or looks like then maybe I can help you or you can take it to an appraiser. If it is a symbol and not a series of letters then this is probably the hallmark (manufacturers logo).
Hope this helps, Susu