1, pebbles
Pebbles are by-products of yellow sand mining, so they are named after being shaped like goose eggs. As a kind of pure natural stone, pebbles are taken from the gravel mountain produced by the uplift of the ancient river bed after the crustal movement thousands of years ago, and they are constantly squeezed and rubbed during the transportation of mountain torrents and running water. In the course of tens of thousands of years, pebbles have experienced the movement of waves and water, lost their irregular edges and corners by the collision and friction of gravel, and been buried underground with sediment for millions of years.
2. Limestone
The main component of limestone is calcium carbonate (CaCO3). Lime and limestone are widely used as building materials.