What is the difference between eluvium and alluvium? I was reading about kimberlite on Wikipedia and it mentioned eluvium. I've heard of alluvium, alluvial fans, alluvial deposits, etc. However, when I looked up eluvium, it sounded exactly like alluvium.
Indeed, looking at the Wikipedia articles, the definitions sound identical to my (expertly untrained) ears:

Alluvium: loose, unconsolidated (not cemented together into
a solid rock) soil or sediments, which has been eroded, reshaped
by water in some form, and redeposited in a non-marine setting.
Eluvium: geological deposits and soils that are derived by in
situ weathering or weathering plus gravitational movement or
accumulation.

So, both of these sound like soil and sediments, eroded and deposited. But obviously, they can't be the same thing.
What's the difference? How can I tell the difference if I see it &quot;in the wild&quot;?
Both are very similar, as they are based on minerals undergoing erosion and the presence of water in the erosion and deposition cycles, the difference is quite subtle, an example is defined in the Gold Prospecting in Western Australia website Alluvial Gold and Eluvial Gold as being

Alluvial deposits are mixed with other deposits and are washed downstream in rivers or transported in among other sediments with water as its medium. An example is that gold deposits this way are smoothed and are ground down the further from the source.

Eluvium deposits are in situ or very near its source, rather than been washed away by water.  For example, eluvial gold are often large nuggets nearer to its source.

A much more succinct definition is provided by the Australian Museum:

Alluvium:


  Detrital material which is transported by a river and usually deposited along the river's pathway, either in the riverbed itself or on its floodplain.


Eluvial:


  Weathered material still at or near its point of formation.