Quadra Sigma III was the formerly inhabited third planet of the Sigma III solar system. In the mid-24th century, this was the home to a Federation mining colony. In 2364, there were 504 colonists.

In that year, the Quadra Sigma III colony transmitted a distress signal for urgent medical help when an explosion resulting from a methane-like gas seeping from underground devastated a mining operation there. The USS Enterprise-D was fortunately close enough to render assistance to the survivors. Soon after rescuing the survivors, the colony was abandoned. (TNG: "Hide and Q")

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