[INST] Are there gems that look extremely similar to diamonds but are worth much less? Other than cubic zirconia. [/INST]Here’s an example, this is an emerald and this is a very similar looking diamond.</s>[INST] Ah, so emeralds can mimic diamonds? Are there any less expensive? [/INST]
Yes indeed. There are also other options like white topaz, white sapphire or even costume jewelry that might be more affordable yet gives a similar look to diamond.
If you’re searching for a stone that looks exactly like a diamond but is cheaper, you’re probably going to be disappointed.  They can be found, but I would not recommend them, as they’re likely to break.