See pyroxenoid group.
See pyroxenoid group.
An obsolete varietal term for phlogopite, biotite.
An obsolete varietal term for phlogopite, biotite.
An obsolete varietal term for a banded form of green serpentine.
A discredited name for allophane from Gräfental, Thuringia, Germany.
A discredited name for an iron-rich, Si-poor chlorite.
See chlorite
See tobermorite.
The structure of romanechite, (Ba,H2O)2(Mn4+,Mn3+)5O10, forms large, rectangular-shaped tunnels bounded by double- and triple-chains of edge sharing MnO6 octahedra. The Mn3+ cations are located in the octahedra at the edges of the triple chains, and the Ba and H2O are located in the tunnels, often in a ratio of 1 to 2. Romanechite occurs in oxidized zones in Mn-rich ore deposits.
A dioctahedral member of the true mica group. The end-member formula is KV2vAlSi3O10(OH)2, where v = vacancy. Roscoelite occurs as a 1M polytype and more rarely as 2M1. Roscoelite is found in sedimentary rocks where V has been remobilized from black shales and mafic rocks. Roscoelite is known from the Colorado Plateau district (Colorado, also Utah, Arizona, New Mexico, USA) in U-bearing sandstones. It is also known from Gabon, Western Australia, and Ontario, in the latter occurrence, the V was introduced from metasomatic fluids.
See rotation symmetry.