A primary deposit is defined as which of the following?

• A. Gems are found in the host rock that carried them to the surface.
• B. Gems are found away from their source.
• C. Gems are found only in surface soils.
• D. Gems are laboratory-created.

Answer: (A)

In a primary deposit, gemstones are still found in the rock where they formed—the host rock that carried them toward or toward the surface. This means the gem remains tied to its original matrix and hasn’t been separated and transported far from its source. This contrasts with secondary (placer) deposits, where weathering and erosion have removed gems from their original rock and concentrated them in other locations like riverbeds or soils. Laboratory-created gems are not natural deposits at all, so they don’t describe a primary deposit. Diamond-bearing primary deposits, for example, occur in the host rock such as kimberlite pipes, where the diamonds crystallized and remained attached to their matrix.