Romanechite
Mineral (Ba,H2O)2Mn5O10
Also called Psilomelane
About it
Hard black botryoidal crusts and stalactites with a brownish-black streak, often banded and polished. Much material sold as psilomelane is romanechite; named for Romanèche-Thorins, France.
- Type
- Mineral
- Group
- Oxide, manganese oxide
- Formula
- (Ba,H2O)2Mn5O10
- Hardness (Mohs)
- 5–6
- Specific gravity
- 3.7–4.8
- Streak
- brownish black
- Lustre
- submetallic, dull
- Crystal system
- Monoclinic
- Colours
- black, dark steel grey
- Transparency
- opaque
- Cleavage and fracture
- none; conchoidal to uneven fracture
Typical values: real specimens vary. For more, see mindat.org.