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khmaralite

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Journal Article
Published: 01 February 2009
American Mineralogist (2009) 94 (2-3): 270-282.
... configurational entropies for the simulations. The substantial SRO present is shown to reduce Sconfig by only 17–18%.Khmaralite is related to sapphirine but contains ca. 1.5 Be per 12 tetrahedra and shows different LRO of {Be, Al, Si}. The minority cation Be is concentrated in Q3 sites. If the exchange enthalpy...
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Journal Article
Published: 01 February 2004
American Mineralogist (2004) 89 (2-3): 327-338.
... Be increases with P, following the MBeAS univariant reactions involving (sapphirine + surinamite + orthopyroxene + chrysoberyl + forsterite or spinel).Natural assemblages containing sapphirine and its Be-rich near-analog khmaralite from the Napier Complex, Enderby Land, East Antarctica formed at higher T (900...
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Journal Article
Published: 01 August 2002
American Mineralogist (2002) 87 (8-9): 1104-1112.
... are dominantly the 1A polytype but lamellae of a 2M phase are consistently present. This is the first 2M sapphirine synthesized in the laboratory, and the first known to be devoid of Fe2+. No superstructure reflections corresponding to the doubled tetrahedral chain repeat of khmaralite were observed, probably...
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Journal Article
Published: 01 October 1999
...Jacques Barbier; Edward S. Grew; Paulus B. Moore; Shu-Chun Su Khmaralite, Ca (sub 0.04) Mg (sub 5.46) Fe (super 3+) (sub 0.12) Fe (super 2+) (sub 1.87) Al (sub 14.26) Be (sub 1.43) B (sub 0.02) Si (sub 4.80) O 40 , is a new mineral closely related to sapphirine from Khmara Bay, Enderby Land...
Journal Article
Published: 01 October 1999
American Mineralogist (1999) 84 (10): 1650-1660.
...Jacques Barbier; Edward S. Grew; Paulus B. Moore; Shu-Chun Su Khmaralite, Ca (sub 0.04) Mg (sub 5.46) Fe (super 3+) (sub 0.12) Fe (super 2+) (sub 1.87) Al (sub 14.26) Be (sub 1.43) B (sub 0.02) Si (sub 4.80) O 40 , is a new mineral closely related to sapphirine from Khmara Bay, Enderby Land...
Journal Article
Published: 01 August 2008
Mineralogical Magazine (2008) 72 (4): 839-876.
... site with most shared edges, M7, at which the dominant cation is most often Ti (aenigmatite, rhönite, makarochkinite), Fe3+ (wilkinsonite, dorrite, høgtuvaite) or Al (sapphirine, khmaralite); much less common is Cr (krinovite) and Sb (welshite). At the fourth level, the two most polymerized T sites...
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Back-to-back <b>khmaralite</b> chains, with interconnecting octahedra. Beryllium c...
Published: 01 February 2009
F igure 7. Back-to-back khmaralite chains, with interconnecting octahedra. Beryllium content of tetrahedra indicated by diagonal shading, Fe 2+ content of octahedra by reverse shading, Si content of tetrahedra by background tone. ( a ) Khmaralite occupancy pattern. Note juxtaposition
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Crystal structure of <b>khmaralite</b>. Numbering of sites corresponds to column 1...
Published: 01 August 2008
F ig . 2. Crystal structure of khmaralite. Numbering of sites corresponds to column 1 of Table 3 (cf. column 1, Table 2 ). Oriented to facilitate comparison of site numbering with that in the makarochkinite structure shown in Fig. 3 . Green tetrahedra: Si, Si >> Be > Al or Si > Al
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Location of sapphirine&#x2F;<b>khmaralite</b> within the MBeAS tetrahedron, and composi...
Published: 01 August 2002
F igure 1. Location of sapphirine/khmaralite within the MBeAS tetrahedron, and compositions of starting mixtures used in this study (solid circles), 7:9:3 or Mg 3.5 Al 0 Si 1.5 O 20 and 3:5:1 or Mg 3 Al 10 SiO 20 (gray), and type khmaralite (hachured). Details of compositions A–N are provided
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[010] 2M  diffraction pattern from sample C, showing no <b>khmaralite</b> superstr...
Published: 01 August 2002
F igure 5. [010] 2M diffraction pattern from sample C, showing no khmaralite superstructure spots (cf., Christy 1988 ).
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The crystal structures of “makarochkinite” and <b>khmaralite</b>; (a) “makarochkin...
Published: 01 January 2002
Figure 10. The crystal structures of “makarochkinite” and khmaralite; (a) “makarochkinite” projected onto (001); note the chains of BeO 4 and SiO 4 tetrahedra extending parallel to the a -axis; (b) “makarochkinite” projected onto (100); circles in (b) represent interstitial Ca atoms; (c
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Crystal structure of <b>khmaralite</b> showing the relationship between sapphirine...
Published: 01 January 2002
Figure 2. Crystal structure of khmaralite showing the relationship between sapphirine (Spr) and khmaralite and occupancies of the tetrahedra sharing three corners with other tetrahedra (the so called Q 3 tetrahedra). Italics emphasize the alternation of ordering schemes from one sapphirine
Journal Article
Published: 01 January 2007
American Mineralogist (2007) 92 (1): 80-90.
... potentials. Welshite can accommodate up to 3.46 Be per 40 O atoms by including several T sites with 100% Be occupancies without the formation of unfavorable tetrahedral Be-O-Be linkages that would result in the related centrosymmetric structures of sapphirine, khmaralite, makarochkinite, and høgtuvaite, none...
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( a ) The topology of nearest-neighbor links in cyclicized versions of the ...
Published: 01 February 2009
F igure 4. ( a ) The topology of nearest-neighbor links in cyclicized versions of the sapphirine and khmaralite chains. ( b ) Topology of next-nearest neighbor links.
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Calculated Si contents ( a ) and Be contents ( b ) of T1-T12 as a function ...
Published: 01 February 2009
F igure 8. Calculated Si contents ( a ) and Be contents ( b ) of T1-T12 as a function of total Be, assuming interaction parameters that best fit khmaralite LRO at 1.5 Be per 12 tetrahedra.
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(a) A planar section of compositional space in the MgO-BeO-Al 2 O 3 -SiO 2 ...
Published: 01 January 2002
Figure 3. (a) A planar section of compositional space in the MgO-BeO-Al 2 O 3 -SiO 2 system showing the relative positions of the beryllian sapphirines synthesized by Hölscher (1987) and khmaralite with Fe 2+ combined with Mg and Fe 3+ combined with Al (modified from Christy et al. 2002 ).
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(b) Composition of natural and synthetic sapphirine for which ion microprob...
Published: 01 January 2002
al. 2000 , their Fig. 12). The dashed line marking a tentative boundary between khmaralite and sapphirine in natural material is based on the appearance of superstructure reflections in a natural sample containing 0.52 Be/20 O ( Grew et al. 2000 ). Type khmaralite, other “Zircon Point”, Gage Ridge
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( a ) Open-branched  vierer  chain of sapphirine, showing cation site label...
Published: 01 February 2009
F igure 1. ( a ) Open-branched vierer chain of sapphirine, showing cation site labels and long-range cation ordering scheme. Darker tones indicate higher Si content. ( b ) The long-range tetrahedral cation ordering pattern of khmaralite. Darker background tones indicate higher Si, whereas
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Diagram of the presumed crystal structure of welshite, which is taken from ...
Published: 01 October 2001
is the oxygen bridging the two most highly polymerized tetrahedra T 1 and T 4, where Be resides in khmaralite and ‘makarochkinite’.
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Compositional plots for Si-rich sapphirine from South Harris, which is pres...
Published: 01 October 2000
F igure 4. Compositional plots for Si-rich sapphirine from South Harris, which is presumed to be beryllian. Khmaralite composition is from Barbier et al. (1999) . Ratios refer to proportions of (Mg, Fe, Mn, Ca)O, (Al, Fe 3+ , Cr) 2 O 3 , and SiO 2 in sapphirine, e.g., 2:2:1 corresponds to 2