admin answers:
You would want to look into the strength and durability of carnelian and see if it's a good choice in those arenas.
I think it would be perfectly comfortable as a band or as a stone in a band.
Obviously, the stone in the metal band will give you more of an engagement ring look, but it's up to you.
I would suggest you try on lots of rings, even buy cheaper versions and wear them around and see how they feel. Consider your lifestyle and take into account how long you expect to wear these rings, will you upgrade in 5 years or do you expect to die in these rings or to be able to pass them down through your family? And try not to go too crazy and spend months debating with yourself over what you actually want (like me!).
If you're open to other ideas, tungsten is becoming a very popular metal for men's bands, and is quite cheap. For yourself, titanium is very cheap and there are more women's designs now than ever.
Of course, there's Gold, 10k or 14k will be your more affordable options. If you like platinum, palladium is its cheaper sister metal. I would avoid sterling silver which is a little too cheap for wedding jewelry and should be left to costume jewelry. Sterling silver might be fine if you're willing to upgrade after a short period.
As far as a stone, sapphires are a great choice, this includes rubies. They're very hard and can handle daily wear. Emerald isn't such a great choice as it is softer and more susceptible to damage. You could always get another stone in an emerald colour, however. I love moissanite and it's what I've chosen, more beautiful than a diamond and at a fraction of the price.
If you're open to CZ make note there are different grades from A-AAAAA. Anything over AAA is excellent quality and will hopefully last your lifetime, though CZ is prone to clouding over time. A and AA CZ are very inexpensive, but may need to be traded out in a year or two. Maybe you might want to get a cheap CZ to start and then just upgrade the stone to whatever when you're in a better financial position. You might be interested in checking out the various gemstones, including carnelian, here: http://www.gemselect.com/group/gemselect.php?x_ByType=on
And a better choice might be waiting until you're done school and can afford a great ring to start with.
Good Luck!