What is a key characteristic of gems found in eluvial deposits?

The key characteristic of gems found in eluvial deposits is that they are located away from the source rock. Eluvial deposits are formed through the weathering and erosion of gems from their original source, typically in situ or primary deposits. As these gems are eroded by natural forces, they are transported to different locations, often settling in areas where they can accumulate.

This movement away from the source rock is significant because it helps define the nature of eluvial deposits, distinguishing them from other types of deposits like alluvial deposits, where gemstones are transported by water. The characteristics of eluvial gems can also reflect the geological conditions of their transport and deposition, which may influence their size and quality compared to gems still near their primary source.

In contrast, the options that imply gems are larger, remain near the source, or are artificially enhanced do not accurately reflect the natural process of eluvial formation and the behavior of these gems within their geographical context.