An obsolete term for poorly defined material, impure halloysite.
An obsolete term for poorly defined material, impure halloysite.
An obsolete term for low-Si chlorite.
An obsolete manganese oxide name, now known as cryptomelane, see hollandite. Also, a term used to describe any massive, gray to black, hard, fine-grained manganese oxide material. Often, the latter material is romanechite.
Cf., wad, romanechite
A poorly defined material, possibly a decomposition product of hornblende consisting of mica and alkali pyroxene.
A poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite or an iron-rich clinochlore.
An obsolete term for fine-grained muscovite or illite.
An obsolete term for fine-grained muscovite or illite.
See hydrotalcite group.
Pyrochroite, Mn(OH)2, structurally forms sheets of Mn(OH)6 octahedra and is isostructural with brucite. The structure is hexagonal closest packed. Pyrochroite occurs in low-temperature hydrothermal environments.
Cf., brucite