MIMETITE

ABOUT THE SPECIMEN

Mimetite from San Pedro Corralitos will always hold a place as some of the most recognizable and ultra desirable locality pieces around. This one is artistically formed and, as shown in the photos, displayable from multiple positions and angles, each with its own point of emphasis. On the front are larger botryoids of a deeper orange color, partially covered by smaller ones and accented with crystals of glistening calcite. What is shown here as the backside has a denser coverage of flashy yellow mimetite, showing more of that classic, splendid rolling luster. Save for some barely noticeable contacting along one edge, the specimen is in marvelous condition (also worth noting that some stabilization was done on the side). Gorgeously showy and exceptionally unique specimen from the legendary one-time 1969 find.

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The San Pedro Corralitos district sits among low desert hills in northern Chihuahua, where Cretaceous limestone and shale were intruded by a granodiorite laccolith forming San Pedro Peak, with later diorite and hornblende andesite porphyries facilitating the fissuring that controlled ore emplacement. The Leon Group contact replacement bodies hosted galena-dominant primary mineralization, and mimetite formed in the oxidized zone above as descending groundwaters dissolved galena and scavenged arsenate from the country rock, precipitating the lead arsenate chloride on goethite gossan matrix. A single pocket encountered in 1968 produced essentially all the collector-grade material known from the site - botryoidal spheroids of saturated yellow-orange, the color a product of lead and arsenic interactions in the crystal structure rather than any trace impurity, building across dark limonite in masses up to roughly 25 cm. The high-luster surface, composed of microscopic crystal points covering each botryoid, is extraordinarily prone to bruising, meaning truly pristine examples are a small fraction of surviving pieces. Benny Fenn brought the material to market at the time for a few dollars per pound; the subsequent recognition that the find would never be repeated drove prices sharply upward over the following decades, and cabinet-scale pristine specimens are now genuinely scarce.