Stellaris - Unlocking Lithoid Crystals Plant (Whispers in the Stone Archaeological site)
Whispers in the Stone Archaeological site unlocks the Lithoid Crystals Plant which upgrades the Synthetic Crystal Plant buildings to produce three Translucer Jobs for a grand total of 6 Rare Crystals per building at the base cost of 3 Energy Building Upkeep and 30 Minerals Jobs Upkeep.
It’s remarkably efficient and the only drawback is it is locked behind a site you may not be able to claim; since you are not guaranteed to have it spawned within your borders.
AI Empires seem to complete excavations pretty fast once they discover a site so even if you conquer the planet when it spawned there is a good chance it has been already fully excavated.
However if you manage to complete Whispers in the Stone your Rare Crystals production will be remarkably boosted.
To be honest there should be a way to generate Archaeological sites via Console Commands but it need to be done very early in the game because once the site has been generated somewhere in the galaxy it can’t be generated again. I will test this soon and