Artifacts are usually crafted from recipes, rather than found. Recipes can be obtained in various ways. To craft an artifact, any types of resources may be required, primarily gems.
Recipes - a special type of items, allowing players to create an Artifacts, using the resources indicated in it.
Recipes can be found in different places and under different conditions in the world, individual for every recipe.
Once you collected the recipe, it's added to your Recipe Book. If you get the same recipe again, it breaks to 1/3 of it's required resources. Some recipes may require special Workbenches.
Presumably, after the disappearance of the Ancients their knowledge (in the form of scrolls) was consumed by plants and creatures. There are also stone tablets, that can be found deep in the rock of caves.
Ancients were kind (or practical) enough to write them with magical runes using Link Gems in the process so that the blueprint itself is a conductor of magic. It means that you only need to put the required resources next to the blueprint, and it will create the Artifact automatically.