Here is the answer to questions about how I'm working with stones, what materials I'm using and some other things^^
You can see on this photo: a tiny round synthetic brush (№000), a stone ( agate, 4x6cm) and tempera paints. Do you see the drops of water on a brush handle? ))
<Update> After painting is ready, I cover it by a special lacquer to protect painting from damage.
Stages of this drawing: 1) sketching on a paper 2) 1 layer by lacquer on a stone 3) lineart with semitransparent layer of paints (usually, it's white, on this painting too) 4) coloring (layer of basic colors) 5) shades and highlights 6) small and tiny details are added 7) Lacquer (2-5 layers, sometimes I cover stone by lacquer on basic colors stage for better protection)