This one was more of a challenge than the others. It is an HDR, tone-mapped from 7 flatbed scanner exposures. The scanner was set to Transparency mode and the black / white points and mid range exposure was adjusted for each scan to get good exposures from all of the varying densities of the translucent minerals.
I also took a single scan in Reflected mode to get detail in the outermost rings of the pattern. This was blended with the HDR in Photoshop. Because the HDR had some flaring effects around the edge of the stone, I created a mask to clamp the tones and give a sharper edge. I placed the result on a black background to accentuate the stained glass glow of this agate.
This is another in a series of experiments on using a flatbed scanner as a macro capture device