An obsolete varietal term for biotite.
An obsolete varietal term for biotite.
A dioctahedral member of the true mica group. The end-member formula is (NH4)Al2 vAlSi3O10(OH)2, where v are vacancies. Tobelite-1M (space group C2/m) was first described from Tobe, Japan by Higashi (1982). Single crystal X-ray analysis of tobelite showed the polytype to be 2M2 in space group C2/c (Mesto et al., 2012). Other polytypes (e.g., 2M1, 3T, 2O) are known. Tobelite and most NH4-rich micas form from diagenesis or in low grade metamorphic or hydrothermal environments, although suhailite is believed to occur at much higher temperatures, in gneisses.
Cf., suhailite
A mineral and mineral group name for a class of hydrated calcium silicate minerals with a strong resemblance to clay minerals, including variability of basal spacing with H2O content, specific surface area, crystallinity, cation exchange (especially with Al substitutions), and polytypism. For example, tobermorite 9Å (chemical composition of Ca5Si6O16(OH)2), tobermorite 11Å (general formula of Ca4+xSi6O15+2x(OH)2-2x . 5H2O), and tobermorite 14Å (Ca5Si6O16(OH)2 . 7H2O; = plombièrite) refer to variations in basal spacings (d(002) values) and different degrees of hydration, which by successive heat treatments ultimately result in progressive dehydration (= “normal” tobermorite) to tobemorite 9Å. Some tobermorite 14Å samples do not dehydrate and are referred to as “anomalous”. Clinotobermorite also topotactically dehydrates upon heating to tobermorite 9Å. Tobermorites have sheets of 7-fold coordinated Ca polyhedra parallel to the (001) and silicate wollastonite-like tetrahedral chains, which link adjacent sheets in tobermoreite 9Å, forming parallel to the b axis (Merlino et al., 1999). The tetrahedral chains form double-width chains in tobermorite 11Å and clinotobermorite, and the double-width chains form zeolitic-type sites for Ca and H2O. Tobermorite is found in hydrothermal altered carbonates (skarns) and basalt vesicles. The tobermorite group is important in cement hydration. Other hydrated calcium silicate phases are also important in cement formation, including an amorphous cement gel (e.g., Ca3SiO5 and cation substituted forms). Other hydrated calcium silicate minerals include jennite (Ca9Si6O18H2(OH)8 . 6H2O) and metajennite, riversideite (?Ca5Si6O16(OH)2), and foshagite (Ca4Si3O9(OH)2).
See calcium silicate hydrate (CSH) in Part 1
Todorokite, (Ca,Na,K)0.3-0.5(Mn4+,Mn3+,Mg)6O12 . 3-4.5H2O, is comprised structurally of edge-sharing triple chains of MnO6 octahedra which form tunnels of widths of three octahedra per wall (Post and Bish, 1988). The triple chains are connected by corner sharing. In addition to the 3 by 3 square tunnels, defects are common with tunnel sizes of 3 x 4, with variations to 3 x 9. Octahedra at the edges of the triple chains contain medium size cations, such as Mg or Mn3+, whereas tunnel cations are the larger cations, H2O, and impurity cations. Todorokite occurs commonly in marine nodules, natural coatings, in oxidized portions in Mn ore deposits, and less commonly, in soils.
A kaolinite-rich rock formed by alteration of glassy volcanic ash or tuff deposited in an organic-rich aqueous environment, such as those associated with coal-forming environments.
A geometrically fixed intergrowth between a reactant and one or more of its products which resulted from a solid-state transformation. Different authors have suggested that the product phase(s) should maintain orientation a) of most atom positions or b) of symmetry axes of the reactant phase. c) The reaction involves conversion throughout a single crystal.
Cf., epitaxy, syntaxy
An obsolete varietal term for manganoan greenalite (or magnesian caryopilite).
A regular interstratification of dioctahedral chlorite-like layers and smectite-like layers in a ratio of 1:1. Tosudite must be dioctahedral on average, although tosudite may refer to smectite-like components that are of dioctahedral or trioctahedral character. Dioctahedral chlorite may be of the type di,dioctahedral or di,trioctahedral interstratified with either dioctahedral smectite-like or trioctahedral smectite-like layers. (Bailey, 1982; Frank-Kamenetskii et al., 1965).
Mineralogical term: an element found in small quantities in a mineral and not considered essential because it is not required for the structure to exist. A trace element is not quantitatively defined, but is generally considered to be <1wt. %. b) Medical/biological term: an element that occurs in animals or plants in small quantities and is required for physiological health. Cf., essential trace element
The phenomenon by which primary minerals in general, and chain silicates and phyllosilicates in particular, alter usually by weathering to secondary minerals through the direct incorporation and reuse of some part of the structure of the parent mineral. Products of transformation reactions are often pseudomorphous or alteromorphous after the primary reactant (parent) mineral, and often exhibit regular crystallographic and orientation relations with the reactant mineral.
See neoformation, inheritance