A poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite.
A poorly defined material, found as infillings in cavities in basic igneous rocks, possibly an altered chlorite.
A glazed or unglazed ceramic plate made by firing milled clay (e.g. kaolin) and quartz, plus added feldspar, carbonates, and/or fluorite. Tiles are commonly used in roofing, walls, floors, mosaics, and art.
Cf., ceramic, glaze, earthenware, stoneware, kaolin
An obsolete varietal term for biotite.
An obsolete varietal term for biotite.
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.