Heterogenite, Chrysocolla
Co3+O(OH) -The formula HCoO2 may be more correct,
Cu2-xAlx(H2-xSi2O5)(OH)4·nH2O
Locality:
L'Etoile du Congo Mine (Star of the Congo Mine; Kalukuluku Mine), Lubumbashi (Elizabethville), Katanga (Shaba), Democratic Republic of the Congo
Field of View: 50 mm
Botryoidal heterogenite (black) on botryoidal chrysocolla (blue-green). The heterogenite aggregates look just like blackberries!
Benjamin Oelkers' Photo
Abstract from Burlet et al. (2016): "Heterogenite is commonly referred in mineralogy literature as a cobalt oxy-hydroxide CoO(OH). However, detailed analysis of Raman and infrared spectra acquired on particularly well-crystallized natural samples of heterogenite suggests that the mineral can be characterized by a delafossite-type structure, with a general chemical formula ABO2. Indeed, the Raman spectrum of heterogenite, along the one with grimaldiite (HCrO2), lacks visible free OH-group vibrational modes, while the infrared spectrum shows strong hydrogen bond absorption bands. HCoO2 is thus a better formulation of heterogenite that describes more clearly its vibrational behavior and avoids the confusion in literature. “
