Depends on how you look at it. Most of central Florida is phosphate mines.

Strictly speaking, it's actually much larger than this, but the areas are a complex mix of current and former mines, alongside a huge number of wildlife reclamation areas and other currently maintained areas related to old mining operations.

Somebody with more knowledge of Mosaic's mining operations than me would have to take a stab at why this particular area was marked as a single quarry. It seems to cover multiple active mines, and even then, not completely.

Florida government website on phosphate mines:
https://floridadep.gov/water/mining-mitigation/content/phosphate