Formula: Cu9S5
Reflected/transmitted colour: opaque, polished section grayish blue, varying with quantity of Cu2S or CuS dissolved. Some species have lost their blue colour more or les completely due to admixtures, but remain isotropic. The colour has then turned to grayish white, darker than chalcocite
Pleochroism:
Optical isotropy/anisotropy: polished section mostly isotropic, remains isotropic at normal temperatures, may sometimes show a weak anomalous anisotropy
Optical sign:
Refractive indices:
Birefringence δ/bireflectance: polished section; not present
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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