Layered clay mineral

Talc and Pyrophyllite. Talc (qv) and pyrophjlhte are 2 1 layer clay minerals having no substitution in either the tetrahedral or octahedral layer. These are electrostatically neutral particles (x = 0) and may be considered ideal 2 1 layer hydrous phyUosiHcates. The stmctural formula of talc, the trioctahedral form, is Mg3Si402Q(0H)2 and the stmctural formula of pyrophylUte, the dioctahedral form, is Al2Si402Q (OH)2 (106). Ferripyrophyllite has the same stmcture as pyrophylUte, but has ferric iron instead of aluminum in the octahedral layer. Because these are electrostatically neutral they do not contain interlayer materials. These minerals are important in clay mineralogy because they can be thought of as pure 2 1 layer minerals (106). 

Mixed layer clay mineral (sericite/smectite) is found in Kuroko ore bodies and altered dacitic rocks underlying the ore. This mineral is thought to have formed by the... 

Main gangue minerals of the Se-type deposits comprise quartz, adularia, illite/ smectite interstratified mixed layer clay mineral, chlorite/smectite interstratified mixed layer clay mineral, smectite, calcite, Mn-carbonates, manganoan caleite, rhodoehrosite, Mn-silicates (inesite, johannsenite) and Ca-silicates (xonotlite, truscottite). 

In eomparison, the Te-type deposits contain fine-grained quartz, chalcedonic quartz, sericite, barite, adularia, ehlorite/smectite interstratified mixed layer clay mineral and rarely anatase. Carbonates and Mn-minerals are very poor in the Te-type deposits and they do not coexist with Te-minerals. Carbonates are abundant and barite is absent in the Se-type deposits. The grain size of quartz in the Te-type deposits is very fine, while large quartz crystals are common in the Se-type deposits although they formed in a late stage and do not coexist with Au-Ag minerals. 

Principal gangue minerals in base-metal vein-type deposits are quartz, chlorite, Mn-carbonates, calcite, siderite and sericite (Shikazono, 1985b). Barite is sometimes found. K-feldspar, Mn-silicates, interstratified mixed layer clay minerals (chlorite/smectite, sericite/smectite) are absent. Vuggy, comb, cockade, banding and brecciated textures are commonly observed in these veins. 

Zeolite minerals (wairakite, laumontite etc.), mixed-layer clay minerals and sme-cite occur in the upper part of the propylitically altered rocks (e.g., Seigoshi, Fuke, Kushikino), but they are sometimes poor in amounts. Generally carbonates are more abundant in the mine area as in the Toyoha district. Temporal relationship between the formation of high temperature propylitic alteration minerals (epidote, actinolite, prehnite) and low temperature propylitic alteration minerals) (wairakite, laumontite, chlorite/smectite, smectite) in these areas (Seigoshi, Fuke, Kushikino) is uncertain. 

Seigoshi argentite electrum, pearceite, polybasite, pyrargyrite, stephanite, chalcopyrite, fahore, galena, sphalerite quartz, adularia, inesite, xonotlite, chlorite, mixed layer clay mineral, sericite. calcite, rhodochrosite... 

This information is reported as the percentage that each of the clay mineral type contributes to total identifiable clay mineral content of the noncarbonate clay-sized fraction of the surface sediments. These percentages were determined by x-ray diffraction, which is luiable to identify noncrystalline solids. Using this technique, clay minerals were found to comprise about 60% of the mass of carbonate-free fine-grained fraction. Most of the noncrystalline soUds are probably mixed-layer clay minerals. Carbonate was removed to facilitate the x-ray diffraction characterization of the clay minerals. In some cases, roimd off errors cause the sum of the percentages of kaolinite, illite, montmorillonite, and chlorite to deviate slightly from 100%. 

The aged pillaring reagents were heated to 65 C and 325 bentonite, American Colloid Company, whose major constituent is the layered clay mineral, montmorilIonite, was added. There was always a 5-fold excess of aluminum in solution and the volume of solution per gram of clay was always 45 cc/g or more. The reaction was carried out for 2 hours. The slurry was filtered and the solids washed two times with water, dried, sized, and calcined at 500 C for 2 hours in air. 

Those chlorites associated with mixed layered clay minerals are most silica-rich and have the greatest compositional variations for grains in a single thin section they tend to be iron-rich and aluminous. One chlorite vein was found to transect a glauconite pellet. This chlorite was quite iron-poor indicating attainment of a local chemical equilibrium between chlorite and iron mica upon its crystallization. 

IIYAKA (J.T.) and ROY (R.), 1963. Controlled synthesis of heteropolytypic (mixed-layered) clay minerals. Clays and Clay Min. 10, 4-22. 

Talc and Pyrophyllile. Talc and pyrophyllite are 2 1 layer clay minerals having no substitution in eiflier the tetrahedral or octahedral layer. These are electrostatically neutral particles i t = 0) and may be considered ideal 2 1 layer hydrous phyllosilieates. Talc and pyrophyllite are found in metamorphic rocks that arc rich in Mg and Al. respectively... 

Grim. R.E., Droste, J.B. and Bradley, W.F., 1961. A mixed-layer clay mineral associated with an evaporite. Clays Clay Miner., Proc, Natl. Conf. Clays Clay Miner., 8<1959) 228—236. 

Heckroodt, R.O. and Roering, C., 1965. A high-alluminous chlorite-swelling chlorite regular mixed-layer clay mineral. Clay Miner., 6 83-89. 

Two sediments from the bituminous subunit (NR-10, 151 and 170 m) are almost free of carbonate. Opal and quartz are dominant in these samples and are accompanied by mixed-layer clay minerals, kaolinite and illite. In the most organic-carbon-rich sediment (NR-10, 170.5 m 25.5% C ) opal is present as amorphous opal A and not as opal CT like in the other sample. Furthermore, the carbonate signals in the X-ray diffractogram are extremely broad. This indicates that the minerals in this sediment are diagenetically less altered than those in the other samples studied. 

The three-layered clay mineral montmorillonite (bentonite) is characterised by a low-hydraulic conductivity and a capacity to bind water molecules and positively charged ions (cations). As such, water-saturated compacted bentonite powder is used as a hydrological barrier in areas such as waste disposal, for example around land-fill sites where the desire is to prevent leakage of contaminants from the land-... 

The layered clay minerals can be classified on the basis of the number and quality of the layers ... 

The most important layered clay minerals are listed in Table 1.2 (Mackenzie and Mitchell 1966 Mackenzie 1975). 

In the case of layered clay minerals, isomorphic substitutions occur not only in the tetrahedral layers but in the octahedral layers, too. When Al3+ is in the central... 

These minerals have different stacking of the silica and alumina layers, as well as, incorporating metal hydrates of Na, K, Mg, Al, or Fe between the silica and alumina layers. Clay minerals can also be characterized according to their morphological features including crystal habit (i.e., plates, rods, or rolled-up platelets) stacked in either a house of cards or blocklike aggregates giving a partide-size distribution. 

Lippmann, F. The solubility products of complex minerals, mixed crystals, and three-layer clay minerals. N. Jb. Miner. Abs. 130, 243-263 (1977). 

The most widespread fill material is reddish brown (2.5 YR 4/4, 5 YR 4/4) loam with a minor admixture of relatively large oolitic bauxite pebbles (derived from the Late Triassic - Camian - beds) and coarse clasts of black chert. Pilot X-ray diffraction analysis revealed mostly muscovite/illite, plus mixed-layer clay minerals of illite/montmorillonite type, chlorite plus mixed-layer clay minerals of chlorite/montmorillonite type, calcium montmorillonite, and diaspore plus gibbsite, or just traces of bauxite minerals (Misic, 2000). The mineral composition is not as uniform as might be expected, and further research, intended for application of factorial analysis, is in progress. A potential sediment source area in the present Cerkniscica River basin (Fig. 1) appears obvious at first glance, but similar outcrops of bauxite and chert do also appear at other sites that are not much more remote. 

---