hollandite

hollandite

[′hä·lən‚dīt]
(mineralogy)
Ba(Mn2+,Mn4+)8O16 A silvery-gray to black mineral composed of manganate of barium and manganese; occurs as crystals.
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Caption: Figure 1: Simulated several morphologies of Hollandite Mn[O.sub.2] models, where (a) [alpha]-Mn[O.sub.2] crystal ([Mn.sub.8][O.sub.16]), (b) (100) bulk surface ([Mn.sub.32][O.sub.64], M(100)), (c) (110) bulk surface ([Mn.sub.16][O.sub.32], M(110)), (d) [(100 x 110)] microfacet ([Mn.sub.32][O.sub.64], M[(100 x 110)]), (e) nanorod(I) ([Mn.sub.28][O.sub.56], MNR(I)), (f) nanorod(II) ([Mn.sub.68][O.sub.136], MNR(II)), and (g) nanorod(III) ([Mn.sub.112][O.sub.224], MNR(III)).
One example is hollandite that is dug out of the Italian Alps and shows promise for housing cesium.
It is interesting to note that Ti[O.sub.2] exists in six different polymorphs, namely, rutile (tetragonal), anatase (tetragonal), brookite (orthorhombic), Ti[O.sub.2] (B) (monoclinic), Ti[O.sub.2] (II) (alpha-Pb[O.sub.2]), and Ti[O.sub.2] (H) (hollandite) [56, 57].
Hollandite Ba[([Mn.sup.4+],[Mn.sup.2+]).sub.8][O.sub.16]
Mineralogical composition of the fines at Balaghat and Ukwa mines is similar in nature and consists of Hollandite, Braunite, Psilomelane, Hematite, Apatite and Quartz.
French scientists summarize results from their research into hollandite, zirconolite, zirconolite-base glass-ceramics, and borosilicate glasses as matrices in which to store highly radioactive nuclear waste for a very long time.
The system contains at least four ternary phases: [Ba.sub.x][Zn.sub.x][Ti.sub.8-x][O.sub.16] with the Hollandite structure, [Ba.sub.4][ZnTi.sub.11][O.sub.27], [Ba.sub.2][ZnTi.sub.5][O.sub.13], and [BaZn.sub.2][Ti.sub.4][O.sub.11].
Neth et al., "Synthesis and characterization of Octahedral Molecular Sieves (OMS-2) having the hollandite structure," Chemistry of Materials, vol.
The rarest specimens include scepters, crystals with moveable gas bubbles in fluid inclusions, fuschite inclusions, and star-shaped hollandite inclusions.
One sample gave an XRD pattern that is a fairly good match for hollandite. Another, poorer, pattern is a fair match for cryptomelane, K[Mn.sub.8][O.sub.16]
A sub-district of this district is Animas-Chocaya district, Ferberite Aullagas See Colquechaca Avicaya Cassiterite, jarosite, stannite, vivianite Ayoreita Amethyst, hollandite, smoky quartz Berenguela Cassiterite, pyrite, pyrrhotite, silver sulfosalts Berenguela Apatite, greenockite, quartz, siderite, sphalerite.
Associated minerals are: braunite, quartz, the "violan" variety of diopside-aegirine-jadeite, strontiopiemontite, hollandite, cryptomelane, jadeite, antimony-bearing titanite and arsenic-bearing titanite and arsenic-bearing fluorapatite.