Stones that Make Money
There are several levels of answers to this question.
You can cut and sell a stone like a Spinel, but it is hard to do because most jewelers do not know what it is, and/or do not really have a market for it. Markets change and Spinels are not as unknown as they used to be but are still not a well known gem stone.
Second – You can only make money on stones that you can acquire in the rough or as native cut to be recut.
Notice I did not say cheap, there is no such thing as cheap quality rough, yes you can occasionally get lucky and get a deal, but in general you will have to pay good money for good rough. You should not let this bother you, all you need to know is that you can make money after you have cut the stone(s).
That being said, there are some stones you will not be able to get rough at all, or if you can get them, there is just no profit margin to cut them. A classic example of this is Sapphires, you will very seldom if ever find commercial color (blue, red, pink) rough that you will be able to make money on.
Also, there are some stones that are in such a high demand in the rough that they can be bought commercial cut for about the same price, top Rhodolite is a good example. Although that is changing. So the stones in general that you will be able to cut profitably (at least in my experience) are narrowed down to:
Tourmaline – Tourmaline of all colors is almost always a money maker for me.
Garnet – Always sells well as long as the stones are not too dark.
Peridot – Difficult to get in larger sized rough, but sells well if you can.
Beryl – Aquamarine/Emerald, there are other Beryls that make money but these two are the primary commercial ones. Emeralds are almost always junk and I very rarely cut them because of the treatments and the liability.
Sapphires (limited) – Very difficult to get rough. An option is buying native cut stones and re-cutting them.
Spinels (limited) – Rough is difficult and the stone is not well known. I do well with it in the collectors market.
Topaz (limited) – Not much profit in it, particularly blue. Topaz is cut so cheap over seas that there is no profit for an American cutter.
Quartz – Citrine and Amethyst are always good sellers and main stays of the colored stone market. There are all types of colors and many of them do well in the collector’s market as well as the commercial market.