One of your problems is that the closer you focus, the less depth of field and it's virtually impossible to manually focus accurately with a consumer digital camera. Then when you set it on auto focus, it focuses on the closest part of the subject within the range of the camera's focusing ability, which throws the back of the subject out of focus.

You should be shooting the jewelry on a neutral non colored background. Then you can easily correct color by using the middle eye dropper in Curves and clicking on the background. That will take the cast out and globally correct the color of the piece. You may need to click on different areas until it looks right.

Best type of camera to shoot close ups of anything is a DSLR body with a macro lens. I'm referring to a prime lens, not a zoom with macro capability. Best lighting is the largest soft light source you can afford. I have some suggestions on using the Lowel Ego and Cloud Dome for shooting small objects. The Cloud Dome was designed specifically for shooting jewelry:
http://www.bermangraphics.com/digital-jury-resources/digital-lighting.htm

I don't think it is the zoom range as it is the magnification ratio. A 1/4 inch wide stone will only be 1/4 inch on the medium at a 1:1 ratio. Do you need it bigger?
The picture maybe blurry because you are trying to hand hold the camera and/or the depth of field is not adequate.
If you are putting the stones ON the light box to photograph them, you may be getting flare which looks like blurr. Gemstones, to me, are like glass, which is usually lit indirectly.

Thanks for the quick response. I am using a small lightbox to shoot the photos so I dont think the lighting is an issue. It is all white.

I'll give the color correction tool a try.

I don't need it any bigger. I guess it's a depth of field issue. The picture isn't really blurry, it just not sharp/crisp. It looks dull. I do use a tripod. I'm putting the stones inside the lightbox to eliminate any shadows so it is surrounded by white when I photog it.

My thinking was that the cuts of the stone would be more obvious the closer I can get with the camera so maybe I do need it bigger because when I open the picture, it opens at 43% of the actual size to fit on my widescreen 15.4" laptop. Then I crop it and the stone looks huge and some distortion is visible so then I resize the image to 40% which gives me a nice approx. 3"x3" photo and the distortion is almost unnoticeable.

Thanks.

If they're shot on white, use the white point eyedropper in curves like I suggested before with the gray point eye dropper. If you double click on the eye dropper you can change the white point to not blow out detail. Change the white RGB settings to 240, 240, 240 or 245, 245, 245. That will clean up your whites while correcting the color. Click on the brightest area you still want to hold detail.