CHRYSOBERYL

ABOUT THE SPECIMEN

Two large crystals of golden-green chrysoberyl, intergrown at the base and each well isolated at the top. Both of them display sixling twinning, on top of showing great luster and gemmy areas.  This twinning is textbook for chrysoberyl, though to find two crystals of such large size that display it on one piece is rare. By visual profile I'd place it as coming from finds of the mid 90's. Ex Jack Halpern and Gene Schlepp.

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Pancas sits within the Eastern Brazilian Pegmatite Province, where Neoproterozoic granitic bedrock hosts pegmatites formed during the post-collisional stage of the Araçuaí orogen between roughly 535-490 Ma. The chrysoberyl specimens that appeared primarily in the early 1990s are distinguished by their cyclic twinning - particularly V-shaped twins that can reach exceptional sizes up to 22 cm in length, though most fine specimens range between 2-5 cm. These twins result from repeated intergrowth on the {110} plane at approximately 60-degree angles, creating pseudohexagonal sixling forms where three individuals each occupy 120 degrees of the cyclic arrangement. The crystals typically display olive-green to honey-yellow coloration with glassy luster and varying degrees of translucency, often showing characteristic feather-like striations on termination faces. What makes Pancas material crystallographically significant is the frequency of complete, undamaged floater specimens - crystals that formed unattached in pocket cavities and show sharp terminations all around. While other Espírito Santo localities like Santa Teresa and Colatina produced chrysoberyl during Brazil's mid-20th century "golden era" of gem crystal recovery, Pancas remained less systematically exploited and is consequently less known to collectors despite producing some of the largest and most perfectly formed twinned specimens from the province.