Historically, the only known diamond sources for more than 2,000 years were from which type of deposits?

Historically, the only known diamond sources for more than 2,000 years were from which type of deposits?

• A. Alluvial
• B. Marine
• C. Primary
• D. Kimberlite

Answer: (A)

Diamonds were long found where water had moved and settled them—in alluvial placers, such as river gravels and floodplains. These deposits concentrate diamonds as the rock erodes and the diamonds are carried downstream, eventually accumulating in easy-to-access locations that could be mined with simple methods. That made alluvial sources the known and exploited diamond sources for more than two thousand years, especially in regions like India and later Africa. Primary deposits, in contrast, are diamonds still locked inside their host rock, like kimberlite pipes, which require more advanced mining and were discovered and exploited much later. Kimberlite refers to the volcanic rock that can carry diamonds, not a source that ancient peoples identified. Marine deposits are a type of alluvial placer found in coastal areas, but historically the broad and most recognizable source category was alluvial placers in rivers and shores.

Diamonds were long found where water had moved and settled them—in alluvial placers, such as river gravels and floodplains. These deposits concentrate diamonds as the rock erodes and the diamonds are carried downstream, eventually accumulating in easy-to-access locations that could be mined with simple methods. That made alluvial sources the known and exploited diamond sources for more than two thousand years, especially in regions like India and later Africa.

Primary deposits, in contrast, are diamonds still locked inside their host rock, like kimberlite pipes, which require more advanced mining and were discovered and exploited much later. Kimberlite refers to the volcanic rock that can carry diamonds, not a source that ancient peoples identified. Marine deposits are a type of alluvial placer found in coastal areas, but historically the broad and most recognizable source category was alluvial placers in rivers and shores.