Mary-- A lot depends on the quality you want. The current crop of
digital cameras have plenty of resolution for good digital images.
The ease of use and flexibility of an SLR camera is somewhat
affordable and very desirable for taking gemstone closeups.
For semi-professional level photographs up to 8 x 11 inch, a 6 to 8
megapixel Digital SLR camera with a good 60mm (or 100 mm if you only
want to shoot gems) macro (closeup) lens has plenty of resolution
for this use and can be purchased for about $800 to $1000. Add to
that a light box or cloud dome or some such lighting stage-- you can
purchase or devise one yourself. You'll also need some type of
software like Photoshop to edit your images. There are a lot of good
software choices that are more reasonable in price than Photoshop.
With a setup like this, you can get super images + have a great
digital slr for other uses as well.
If you don't want to spend this much, you can get pretty good results
with some of the point-and-shoot cameras, but you really need to
shop it carefully, and be aware of the limitations of these type of
cameras. You'll still need a stage and software.
Here's a small version of one of my favorite shots of a really great
spinel, taken with a Canon digital Rebel SLR, 8 megapixel, 100 mm
macro lens, on an ImageDome stage.