Let me take you through the steps to create realistic pebbles and stones using watercolour I will share with you the techniques I use to represent the texture and depth in this step by step lesson.
Materials required
Set of watercolour paints (Pans or tubes)
Mixing pallet or plate Ruler
Black marker pen or sharpie (felt tip)
2 cups water
Brushes 
Rock salt or table salt,
Paper towels
Cold pressed watercolour paper, textured.
A Hairdryer