Doing a colored round jewel
Start by making a new layer and doing an elliptical selection. Now fill the selection with black (1). Pick dark red for foreground color and black for background. Pick the Radial gradient tool and click on the Options tab and click the Edit button. Now click the New button and name the gradient Jewel. Set the sliders like in the pic below. After doing that, click Finish and do the gradient so that the center (the place you start dragging from) is in the middle of the lower part. Drag the gradient from there to the top of the selection (2).

Now pick the airbrush tool and a big brush and white color. Airbrush a dim spotlight in the upper part (3). Pick a smaller brush and do a new spotlight on top of the dim spotlight, preferrably a bit higher than the original spotlight (4). Then pick orange color and a small brush. Airbrush a small spotlight in the lower part of the jewel (5). If you want you can airbrush a second (smaller) spotlight on top of the lower one (like in the finished jewel below). Now apply Layer Effects and put Inner Glow in the jewel, with Opacity 75%, Blur 2 and Intensity 50. Done (6).