Can gemstones be found in rivers?

Yes, lots of valuable gemstones, like sapphires, rubies, garnets, and diamonds, show up in rivers and streams as alluvial deposits. The stones usually weather out of their original host rocks, then get carried downstream by fast-moving water currents over thousands of years, eventually ending up somewhere new.

When the water quickly wears down the surrounding rock, heavier, very durable crystals settle in riverbeds, gravel bars, and especially the inner bends of swift streams. This process is called alluvial mining, which naturally tumbles and rounds the rough pieces, often removing the more fragile lower-grade material. Some well-known areas, including the gem gravels of Sri Lanka and the diamond-heavy river systems of Sierra Leone, depend a lot on these handy secondary deposits.