Rough stone torn from the earth by the miner, a gem is often cut by the lapidary to end up mounted on a ring, earring or any other jewelry ornament. It can be natural, processed or artificially made (synthetic stone).
Few gems are perfectly pure. Most contain foreign bodies or have various crystallization accidents. These accidents are considered inclusions, which should not be described as "defects", because their presence does not necessarily lead to a depreciation of the gem.
The minerals included may be older than it, and have simply been encompassed during growth. They may also have formed at the same time as the host crystal. Who, as a result of faster growth, included them in his mass. There are, in addition, inclusions that are more recent than the host crystal: they come from liquids that have entered through cracks in the crystal.