Gold from USA, California, Eagle's Nest Mine

This is an old photo I took in early 2019, when I was just starting out in photography. The rock in the picture, the first piece in my core collection, was purchased 8 years ago.

It’s interesting how, when life gets stressful and time feels like it’s flying by, taking a moment to reflect can bring some clarity. This old photo reminds me of the excitement I felt when I first acquired a specimen I had dreamed of for so long. Since then, there have been so many other ‘firsts’ in my life. Now, what keeps me busy is always chasing the next ‘first’.

This is a gold on quartz from Eagle's Nest Mine, one of the most legendary mines of gold specimens in the US. The geology is the also pretty fascinating: gold is a rare chalcophile element (prefers to associate with sulfide phases rather than silicate or metallic phases in geological processes） that is hard to be concentrated by pure magmatic differentiation unless some special fluids (like S-, Cl-bearing) are introduced. Subduction-related orogenic environment is a perfect place to reach that because of its complexity and multiple sources are involved. One possible source of fluid and gold is from devolatilization of a subducted oceanic slab with its overlying gold-bearing sulfide-rich sedimentary package, or the associated metasomatized mantle wedge, with CO2 released during decarbonation and S- and ore-related elements released from transformation of pyrite to pyrrhotite. The source of arsenic may also was derived from sediments.

4cm, Eagle‘s Nest Mine, Sage Hill, Michigan Bluff Mining District, Placer County, California, USA

Jingnan (Tom) Zhang Coll & Photo