Agate is one of my favourite minerals. The natural one is usually brown and grey, although there are more variations, but it can also be dyed in various colours, which I learned to appreciate over time, especially when the dye job looks well. The first one is one of the natural brown slices I brought over from Poland last year. I used malachite beads to compliment it. The other one is a dyed bead, and the colours are sort of reverse (brown on green, not green on brown). Enjoy!