Andradite

specimen number:
2133335

location:
Green Fire Mine, San Benito Co., California, USA

description:
Lustrous green crystals of andradite, this is the variety known as demantoid, to 0.5 cm in size across the top of matrix. Collected by Chuck Trantham.

The Green Fire mine, located on Santa Rita Peak within the New Idria District of San Benito County, California, is a specialized mineral specimen locality renowned among collectors for producing vibrant green andradite garnet crystals, specifically the chrome-rich gem variety known as demantoid garnet. Geologically, the deposit is situated within the New Idria serpentinite body, a massive, tectonically emplaced ultramafic complex consisting largely of altered serpentinite rock. The demantoid garnets and associated minerals, such as diopside, clinochlore, and magnetite, formed through low-temperature hydrothermal alteration and regional metamorphism, where calcium- and silica-bearing fluids interacted with the magnesium- and iron-rich serpentine matrix under high pressure. The history of the Green Fire mine centers on localized, small-scale surface quarrying and trenching specifically targeted at extracting high-quality mineral specimens rather than industrial ore. While the broader New Idria district experienced intensive mercury and asbestos mining from the mid-19th century through the late 20th century, the targeted exploitation of the Green Fire mine for its distinct green crystals emerged primarily during late-20th-century exploration by mineral collectors and independent prospectors, with sporadic, manual specimen recovery continuing on a limited basis into the 2010s and 2020s.

Charles C. Trantham was a prominent California mineral collector, field collector, and geologist whose active field exploration spanned the mid-to-late 20th century. Professionally trained as an engineering geologist, he combined his formal scientific background with a deep passion for field mineralogy, leading him to explore and document numerous remote localities throughout California, Nevada, and the Pacific Northwest. He was widely recognized within the mineralogical community for his methodical approach to collecting, keeping meticulous records of his field discoveries, and assembling an extensive, highly regarded private collection of Western North American minerals. Trantham frequently contributed to the field by discovering or providing rare research material to academic mineralogists, and his legacy is preserved today through the high-quality specimens bearing his original handwritten labels that reside in major private collections and museum archives.

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