Do precious gems maintain their value?

Wrong. Category 

Depends on the gem, I:E: synthetic diamond production has recently become very good, so good that man made ones are actually better quality than natural ones

I bought a 3ct red beryl stone for $10,000 thinking that. I had it appraised immediately and they gave me a number within the same ballpark, actually a bit higher $10,250 I think. A couple of years later I tried selling it to a couple of places just to speculate because I wasn't desperate or pressed or anything and I've gotten low balled BIG time. I got an offer for $7,450 from one buyer. Another one offered me around $8,350. It's all because let's say that the appraisal was correct, if you're a jeweler you know that price is what you're going to be able to charge and thus you need to make a profit SO they will try to lowball as much as they can to get the best possible profit margin in return. at least that's the vibe I got. at the end of it all, I was left with a shiny red stone that I keep stored inside a bank vault. who knows if I'll ever be able to get rid of it but I personally wouldn't recommend. that $10,000 would've been better off invested in stocks or bonds or something else.

They do, they always have but, it's a big target for fraud because not everybody can tell. Be careful.