Structure
Manganese occurs in different states, including Mn2+, Mn3+ and Mn4+. Todorokite is made up of (Mn4+O6) octahedra that share edges to form triple chains. These chains share corners to form roughly square tunnels parallel to the b crystal axis. The tunnels accommodate water molecules and large cations such as potassium K+, barium Ba2+, silver Ag+, lead Pb2+, calcium Ca2+ and sodium Na+. The octahedra at the edges of the triple chains are larger than those in the middle and therefore are likely to accommodate the larger cations (magnesium Mg, manganese Mn3+, copper Cu2+, cobalt Co, nickel Ni etc.), whilst the middle octahedra are occupied by the smaller Mn4+ cations. This structure is similar to that of hollandite (BaMn2+Mn4+7O16) and romanèchite ((Ba,H2O)2(Mn4+,Mn3+)5O10), but with larger tunnels. Although tunnels formed from triple chains of octahedra are most common in todorokite, occasional tunnels have been observed in crystals from both terrestrial and manganese nodule deposits that have one pair of sides formed by triple chains, but with the other pair of sides formed from chains 4, 5, 8 or more octahedra wide.
Read more about this topic: Todorokite
Famous quotes containing the word structure:
“Slumism is the pent-up anger of people living on the outside of affluence. Slumism is decay of structure and deterioration of the human spirit. Slumism is a virus which spreads through the body politic. As other “isms,” it breeds disorder and demagoguery and hate.”
—Hubert H. Humphrey (1911–1978)
“With sixty staring me in the face, I have developed inflammation of the sentence structure and definite hardening of the paragraphs.”
—James Thurber (1894–1961)
“Why does philosophy use concepts and why does faith use symbols if both try to express the same ultimate? The answer, of course, is that the relation to the ultimate is not the same in each case. The philosophical relation is in principle a detached description of the basic structure in which the ultimate manifests itself. The relation of faith is in principle an involved expression of concern about the meaning of the ultimate for the faithful.”
—Paul Tillich (1886–1965)