This park contains trails which take you through historic buildings left over from the Gold Rush Era, where mines were built to mine mercury. Some of the remnants include an old rotary furnace, barns, houses, a mine shaft you can enter, an old tree used for hanging, and other structures that have been badly damaged. Prior to that, in the mid 1800s, the Ohlone Indians had discovered the cinnabar in that location and used it for trading. Eventually, the work force depleted and homes were abandoned. The Civilian Conservaton Corps came in and removed most of the buildings and now there remains little evidence that several towns here once thrived.
Given the history of the location, there really wasn't much activity. The EMF detectors only caught high EMF around the power lines which run right through the park, so that was quickly dismissed. While ghost towns are a great piece of history, it does not automatically imply that the residents are still there, as its name suggests
The location that had the highest potential for activity was inside the mine itself. This is because accidental deaths occur while mining - it's a dangerous job! However, only one mine allowed visitors to enter and it was limited to a couple hundred feet. Even at this short distance, the environment changed drastically. Inside, the air was completely stagnant, and no light penetrated that far, so it was pitch black. The air was also very warm, humid, and heavy. There were a few anomalies captured with video and still camera.
Other than the mine, there was nothing else captured. The historic gravesite wasn't included in this investigation due to the extra distance, so expect to see it in an upcoming one!