This is the 10679th most frequent German word.
rich
The German word "rich" does not exist. You may mean "reich," which translates to "rich" or "wealthy" in English.
In this sentence, 'reich' is used metaphorically to describe a thing (soil) that is abundantly endowed with a particular quality (minerals).
Der Boden hier ist reich an Mineralien.
The soil here is rich in minerals.
Here, 'reich' is part of an adverbial phrase indicating the extensive or lavish manner in which something (the banquet table) was done or decorated.
Das war eine reich dekorierte Festtafel.
That was a richly decorated banquet table.
Here, 'reich' is used as an adjective to describe someone who possesses a lot of wealth or material affluence.