Cryptomelane
Mineral KMn8O16
About it
Hard, black, fine-grained masses and botryoidal crusts that are a common part of 'psilomelane'. Only X-rays tell it reliably from romanechite and hollandite; widespread in weathered manganese deposits.
- Type
- Mineral
- Group
- Oxide, hollandite group
- Formula
- KMn8O16
- Hardness (Mohs)
- 6–6.5
- Specific gravity
- 4.1–4.4
- Streak
- brownish black
- Lustre
- submetallic, dull
- Crystal system
- Monoclinic
- Colours
- black, grey, bluish grey
- Transparency
- opaque
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.