Bay Curious The Mercury Mine That Built a Boomtown Near San Jose
Mar 26, 2026
Rachael Myrow, an investigative reporter who traced the rise and fallout of New Almaden, narrates the story of a once-rich mercury mine. She explains what cinnabar and quicksilver are. She outlines how mercury powered the Gold Rush, recounts ownership battles and legal fights, and highlights the toxic legacy left in the Bay and local cultural traces.
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How Quicksilver Forms And Why It Was Valuable
- Cinnabar is mercury bonded to sulfur and formed 10–12 million years ago in the South Bay during volcanic activity.
- Heating cinnabar releases liquid mercury, which miners used during the Gold Rush to extract gold from crushed rock via amalgams.
Why Mercury Was Critical For Gold Extraction
- Mercury (quicksilver) was essential to Gold Rush extraction because it forms an amalgam with gold that can be heated to recover the metal.
- Linda Will details the process: pour mercury on crushed ore, collect amalgam, heat to 1076°F to vaporize mercury and leave gold.
Castillero's 1845 Discovery That Started New Almaden
- Don José Joaquín [Castillero] discovered red cinnabar near San Jose in 1845 while cataloging Mexican strategic assets.
- He recognized its value because Spain controlled global mercury from Almaden, making local cinnabar a potential fortune.