Every weekend, Chantaburi's gem dealers set up tables along Si Chan Road and the cross-streets that lead off it. From Friday afternoon through Sunday lunchtime, sellers arrive with little folded papers of raw rubies, sapphires, and zircons; buyers sit across from them with electric scales, loupes, and pocket flashlights. Deals are agreed in whispers and counted out in Thai baht.
It is one of the largest coloured-stone trading markets in the world. Casual visitors are welcome to walk through and watch but should not buy unless they really know what they are doing — even experts get fooled. The streets around the market are full of cutting shops where stones are faceted, and the cathedral is two minutes away on foot.