Where it forms, where it's found
- Geological setting
Fumaroles.
- Type locality
- Mount Vesuvius
- Metropolitan City of Naples
- Campania
- Italy
5recorded occurrences
Physical
- Transparency
- Opaque
- Colour
- Black · bluish black
Changes to green colours upon exposure.
- Tenacity
- brittle
- Cleavage
- Perfect
One direction, perfect, probably prismatic
- Density
- 4.08 g/cm³
Optical
- Optical type
- Biaxial
- Notes
Deep brown in transmitted light.
Crystallography
- Space group
- Fddd
- Cell parameters
- a = 9.595(3) Å · b = 9.693(3) Å · c = 7.461(3) Å
- Ratio a:b:c
- 1 : 1.010 : 0.778
- Z
- 8
- Type-locality form
Platy or scaly, to 1 cm.
Crystal structure
Chemical composition
Synonyms
- Melanotallo
- Melanothalliet
- Melanothallite (of Scacchi)
In other languages
- German
- Melanothallit
- Italian
- Melanotallite · Melanothallite
Classification
Strunz
10th ed.3.DA.05
- 3HalidesClass
- 3.DOxyhalides, hydroxyhalides and related double halidesDivision
- 3.DAWith Cu, etc., without PbGroup
- 3.DA.05MelanothalliteSpecies
Dana
8th ed.10.04.04.01
- 10Oxyhalides and HydroxyhalidesClass
- 10.04A2(O,OH)XqType
- 10.04.04— unnamed intermediate level —Group
- 10.04.04.01MelanothalliteSpecies
CIM
—8.2.7
- 8Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and FluosilicatesClass
- 8.2Halides of CuGroup
- 8.2.7MelanothalliteSpecies
Literature, links & citation
Citations
- 1870Scacchi, A. (1870) Dell'eriocalco e del melanotallo, nuove specie di minerali. Rendiconto dell'Accademia delle Scienze Fisiche e Matematiche (sezione della Societa reale di Napoli): 9: 86-89.
- 1884Scacchi, A. (1884) Reale Accademia delle Scienze Fisiche e Matematiche, Naples, Rend.: 10: 158.
- 1935Zambonini, Ferruccio (1935) Mineralogia Vesuviana. second edition with Quercigh, 463 pp., Naples: 111-112.
- 1951Palache, Charles; Berman, Harry; Frondel, Clifford (1951) The System of Mineralogy (7th ed.) Vol. 2 - Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons.
- 1982Bergasova, L.P., Filatov, S.K. (1982) The chemical formula and crystallochemical characteristics of melanothallite, Cu2OCl2. Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva, 111(5), 562-565.
Cite this entry
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Melanothallite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/melanothallite-2623},
note = {Accessed 2026-05-11}
}