Chalcopyrite Disease

Chalcopyrite-disease is a controversial texture. Some have attributed it to exsolution, others to diffusion. In these samples, from Erglodd mine, dark grey early sphalerite is crowded with orientated chalcopyrite needles and also rows of siegenite grains (L, unusual). At Erglodd, the argument for diffusion/ replacement stands strong. The texture is not ubiquitous, but is restricted to sphalerite adjacent to later chalcopyrite veins (R). Chalcopyrite-disease is restricted to the early, complex polymetallic mineralisation. Later sphalerites are squeaky-clean in contrast.

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