Give it with aperture settings of f-11 or higher, and set your ISO as low as possible, preferably ISO 100. Make sure that the white balance is precisely adjusted to capture your jewelry with the colors you want. Choose an aperture value between 16 and 22 depending on the jewel or stone being photographed. You'll benefit from greater depth of field, better sharpness and better reproduction of details.
This is because you're focusing on a smaller part of your jewelry. However, the rest of the image will be blurry. To get sharpness all over the jewel, you'll have to use the software's automatic focus stacking technique (here's our tutorial dedicated to automatic focus stacking).
