Brazil's diamonds are mined predominantly from which deposits?

• A. Kimberlite pipes
• B. Deep mantle sources
• C. Alluvial deposits
• D. Marine placers

Answer: (C)

Diamonds reach miners in secondary deposits when the stones are eroded from their source rocks and transported by water to new places where they settle. In Brazil, the majority of diamond production comes from alluvial (placer) deposits—the gravels and sands in river beds where diamonds have been carried and concentrated over time by streams. These alluvial pockets are extensive across Brazil’s river basins, making them the most productive mining environments there.

Kimberlite pipes are the primary source rocks where diamonds originate, but in Brazil they do not account for the bulk of mining compared with alluvial deposits. Marine placers exist in some coastal areas, but they are not the main source country-wide. Deep mantle sources are the origin of the diamonds, not the mining deposits themselves.