Velara III is a planet where a Federation terraforming project unknowingly threatened an intelligent crystalline life form living beneath the surface.
Velara III is the planet at the centre of Home Soil. A Federation team was terraforming the world, using a drilling process to remove a layer of saline water beneath the surface, and the Enterprise arrived because the project had fallen behind schedule.
The planet turned out to be home to the microbrains, tiny inorganic crystals that formed an intelligence and depended on that saline layer. After they took control of part of the Enterprise to defend themselves, the crew made peace with them, and Velara III was declared off limits to the terraformers.