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About 1000 zircon grains from a diamondiferous quartzofeldspathic rock of the Saxonian Erzgebirge were investigated for inclusions using optical microscopy and confocal laser-Raman spectroscopy. Cathodoluminescence imagery was applied to characterize the growth zone of zircon where the inclusions occurred. The most abundant inclusion minerals are microdiamonds. Coesite was not detected. However, garnet and jadeite occur as rare inclusions in zircon cores where diamonds are lacking. Jadeite was detected for the first time in quartzofeldspathic rocks from the crystalline complex of the Erzgebirge. The compositions of the pristine garnets in the zircons are similar to those of core areas of millimeter-sized garnets but the original garnet composition of the early metamorphic stage is only preserved in zircon. Intracrystalline diffusion at temperatures as high as 1000 [degrees]C resulted, for instance, in higher Ti concentrations in garnet cores compared with garnet enclosed in zircon. Rutile, quartz, and the compositions of jadeite and garnet inclusions in zircon and of phengite inclusions in cores of large garnets were applied for geothermobarometry. The results, related to an early metamorphic stage, are 650[degrees]C and 18 kbar, which represent conditions at the base of a thickened continental crust before deeper subduction.

Peraluminous granites of the Erzgebirge-Fichtelgebirge, Germany, are hosts of various members of the monazite group of minerals that display an unprecedented compositional diversity. The Eibenstock S-type granite constitutes the third reported occurrence worldwide of brabantite and the first occurrence of this mineral in a granite. Many new occurrences of cheralite-(Ce), as well as a monazite-group mineral intermediate between monazite-(Ce) and huttonite for which the term huttonitic monazite is proposed, were discovered. Even 'common' monazite-(Ce) may show extreme ranges of actinide and lanthanide element concentrations. The granites that host brabantite and cheralite-(Ce) are highly differentiated, strongly peraluminous, low-temperature residual melts of S-type affinity, which are rich in fluorine and other volatile constituents but depleted in thorium and the light rare-earth elements. Such highly evolved, volatile-rich compositions resemble rare-element pegmatites and appear favorable for the precipitation of cheralite-(Ce) and brabantite, but not of monazite with large amounts of huttonitic substitution. Instead, these minerals occur preferentially in F-poor biotite and F-rich Li-mica granites of A-type affinity. Irrespective of the level of uranium in silicate melts, which may exceed that of thorium, the substitution of uranium in monazite remains limited. The compositional data reported here are consistent with complete miscibility in the monazite-(Ce)-brabantite solid solution series under magmatic conditions. These granites contain monazites that span almost the entire compositional range reported for monazite-group minerals worldwide, and therefore granites appear to be ideal rocks in which to study the crystal chemistry of this mineral group in general.

Reflected-light microscopy and fine-scale laser microRaman spectroscopy of shocked garnetcordierite-sillimanite gneisses in suevites of the Ries meteorite impact crater, Germany, led to the discovery of impact diamonds in their pristine graphite-diamond assemblages. Graphite-diamond textural relations permit a clear determination of the solid-state nature of the formation of diamond from graphite, which is estimated to have occurred at a peak-shock pressure between 30 and 40 GPa. Shock-induced transformations were promoted only in unkinked and undeformed graphite booklets at the graphite-garnet, graphite-sillimanite, or graphite-rutile interfaces, where the difference in shock impedance is very high. Reverberations of shock waves with short wavelengths similar to the grain sizes at the phase boundaries are probably important constraints for dynamic graphite-diamond phase transformation. Raman spectroscopic investigations of hard transparent carbon platelets intercalated between fine-grained diamond and deformed graphite revealed the platelets to be Raman inactive. The platelets are either dense amorphous carbon or an unknown dense crystalline carbon phase that is Raman inactive.

Obertiite is a new amphibole species from Bellerberg, Laccher See district, Eifel, Germany. It occurs with tridymite, fluororichterite, hematite, futile, aegirine-augite, kinoshitalite, and fluor-apatite in vugs in volcanic rocks, and crystallized from late-stage hydrothermal fluids associated with recent volcanism. Obertiite occurs as pale-pink elongated blades and divergent aggregates. It is brittle, H = 5, [D.sub.calc] = 3.16 g/[cm.sup.3], has a colorless streak, vitreous luster, and does not fluoresce; it has perfect cleavage on {110} and conchoidal fracture. In plane-polarized light, obertiite is slightly pleochroic in shades of pink to red-orange; X ^ a = 2 [degrees] (in [Beta] obtuse), Z = b, Y ^ c = 12 [degrees] (in [Beta] obtuse) with absorption X ~ Y ~ Z. It is biaxial negative, [Alpha] = 1.643(1), [Beta] =1.657(1), [Gamma] = 1.670(3), 2[V.sub.x] = 81(1) [degrees], no dispersion visible. Obertiite is monoclinic, space group C2/m, a = 9.776(2), b = 17.919(3), c = 5.292(1) [Angstrom], [Beta] = 104.05(2) [degrees], V = 899.3(3) [[Angstrom].sup.3], Z = 2. The strongest ten X-ray diffraction lines in the powder pattern are [d(I,hkl)]: 8.414(10,110), 2.705(7,331,151), 3.390(6,131), 4.467(5,040), 3.117(5,310), 2.531(5,202), 3.255(3,240), 2.577(3,061), 2.163(3,171,261), 4.013(2,111). Analysis by a combination of electron microprobe, SIMS, and crystal-structure refinement gives Si[O.sub.2] 54.53, [Al.sub.2][O.sub.3] 0.15, Ti[O.sub.2] 7.75, [Fe.sub.2][O.sub.3] 2.61, [Mn.sub.2][O.sub.3] 3.27, FeO 3.36, ZnO 0.08, MgO 14.13, [Li.sub.2]O 0.05, CaO 0.52, [Na.sub.2]O 9.51, [K.sub.2]O 0.98, F 0.55, [H.sub.2]O 0.20, O [equivalent] F -0.23, Ni, Cr, V, Cl not detected, sum 97.46 wt%. The formula unit, calculated on the basis of 24(O,OH,F) is ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], and is close to the ideal end-member composition Na [Na.sub.2] ([Mg.sub.3][Fe.sup.3+][Ti.sup.4+]) [Si.sub.8] [O.sub.22] [O.sub.2]. The crystal structure of obertiite was refined to an R index of 2.6% using MoK[Alpha] X-ray intensity data. The M1 site is split into two subsites along the b axis, M1 and M1A; the M1 site is occupied by Mg, and M1A is occupied predominantly by [Ti.sup.4+] and [Mn.sup.3+]; M2 is occupied by Mg, [Fe.sup.2+], and [Fe.sup.3+], and M3 is occupied by Mg. Local bond-valence considerations suggest that [O.sup.2-] at O3 is linked to [Ti.sup.4+]Mg or [Mn.sup.3+][Mn.sup.3+] at the adjacent M1 and/or M1A sites, and that OH or F at 03 is linked to MgMg at the adjacent M1 sites.