Which term describes a deposit where gems are eroded from their source rock, transported away from the source and further concentrated?

Which term describes a deposit where gems are eroded from their source rock, transported away from the source and further concentrated?

• A. Bast
• B. Average girdle diameter
• C. Aggregate
• D. Alluvial deposit

Answer: (D)

Think about how a gemstone ends up in river gravels away from its original rock: diamonds resist weathering, so they survive erosion while surrounding material wears away. As water carries these diamonds downstream, they settle and concentrate where the current slows, forming deposits in gravel and sand along streambeds. This describes an alluvial deposit, a secondary concentration of gems eroded from their source. The other options don’t fit: bast isn’t used for diamond deposits, average girdle diameter relates to cut dimensions, and aggregate is just a general collection rather than a transported-and-concentrated deposit.

Think about how a gemstone ends up in river gravels away from its original rock: diamonds resist weathering, so they survive erosion while surrounding material wears away. As water carries these diamonds downstream, they settle and concentrate where the current slows, forming deposits in gravel and sand along streambeds. This describes an alluvial deposit, a secondary concentration of gems eroded from their source. The other options don’t fit: bast isn’t used for diamond deposits, average girdle diameter relates to cut dimensions, and aggregate is just a general collection rather than a transported-and-concentrated deposit.