The recently published method for the structure refinement from threedimensional precession electron diffraction data using dynamical diffraction theory [Palatinus et al. (2015). Acta Cryst. A71, 235-244] has been applied to a set of experimental data sets from five different samples -Ni 2 Si, PrVO 3 , kaolinite, orthopyroxene and mayenite. The data were measured on different instruments and with variable precession angles. For each sample a reliable reference structure was available. A large series of tests revealed that the method provides structure models with an average error in atomic positions typically between 0.01 and 0.02 Å . The obtained structure models are significantly more accurate than models obtained by refinement using kinematical approximation for the calculation of model intensities. The method also allows a reliable determination of site occupancies and determination of absolute structure. Based on the extensive tests, an optimal set of the parameters for the method is proposed.

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Here we report a nomenclature and classification for the seidozerite-supergroup minerals. The TS (Titanium-Silicate) block is the main structural unit in all seidozerite-supergroup structures; it consists of a central O (O = Octahedral) sheet and two adjacent H (H = Heteropolyhedral) sheets where Si2O7groups occur in the H sheets. The TS block is characterized by a planar minimal cell based on translation vectors, t1and t2, the lengths of these vectors are t1 ≈ 5.5 and t2 ≈ 7 Å, and t1 ^ t2 is close to 90°. The forty-five minerals of the sedozerite supergroup are divided into four groups based on the content of Ti and topology and stereochemistry of the TS block: in rinkite, bafertisite, lamprophyllite and murmanite groups, Ti (+ Nb + Zr + Fe3++Mg + Mn) = 1, 2, 3 and 4 apfu (atoms per formula unit), respectively. All TS-block structures consist either solely of TS blocks or of two types of block: the TS block and an I (Intermediate) block that comprises atoms between two TS blocks. Usually, the I block consists of alkali and alkaline-earth cations, H2O groups and oxyanions (PO4)3-, (SO4)2-and (CO3)2-.The general formula of the TS block is as follows AP2BP2MH2MO4(Si2O7)2X4+n, where MH2and MO4= cations of the H and O sheets; MH = Ti, Nb, Zr, Y, Mn, Ca + REE, Ca;MO = Ti, Zr, Nb, Fe3+, Fe2+, Mg, Mn, Zn, Ca, Na; AP and BP = cations at the peripheral (P) sites = Na, Ca + REE, Ca, Zn, Ba, Sr, K; X = anions = O, OH, F, H2O; XO4+n=XO4 +XPn, n = 0, 1, 1.5, 2, 4; XP= XPMand XPA= apical anions of MH and AP cations at the periphery of the TS block.

The volume thermal expansion coefficient and the anisotropy of thermal expansion were determined for nine natural feldspars with compositions, in terms of albite (NaAlSi(3)O(8), Ab) and anorthite (CaAl(2)Si(2)O(8), An), of Ab(100), An(27)Ab(73), An(35)Ab(65), An(46)Ab(54), An(60)Ab(40), An(78)Ab(22), An(89)Ab(11), An(96)Ab(4) and An(100) by high resolution powder diffraction with a synchrotron radiation source. Unit-cell parameters were determined from 124 powder patterns of each sample, collected over the temperature range 298-935 K. The volume thermal expansion coefficient of the samples determined by a linear fit of V/V(0) = alpha(T - T(0)) varies with composition (X(An) in mol %) as: alpha(V) = 2.90(4) x 10(-5) - 3.0(2) x 10(-7) * X(An) + 1.8(2) x 10(-9) * X(An)(2). Two empirical models for the non-linear behaviour of volume with temperature give a better fit to the experimental data. The change with composition in the a degrees parameter of the non-linear Holland-Powell model V/V(0) = 1 + a degrees (T - T(0)) + 20a degrees (root T - root T(0)) is: a degrees = 4.96(5) x 10(-5) - 4.7(2) x 10(-7) * X(An) + 2.2(2) x 10(-9) * X(An)(2). For the Berman model, V/V(0) = a(1)(T - T(0)) a(2)*(T - T(0))(2), the parameters change with composition as: a(1)=2.44(15)x10(-5)-3.1(6)x10(-7)*X(An)+1.8(5)x10(-9)*X(An)(2) a(2)=9(1)x10(-9)-4(2)x10(-11)*X(An) The thermal expansion of all plagioclases is very anisotropic, with more than 70% of the volume expansion being accommodated by a direction fairly close to the (100) plane normal, whereas perpendicular directions exhibit smaller, and in some cases slightly negative or zero, thermal expansion

High resolution single-crystal X-ray diffraction (HR-SCXRD) Analysis (EMPA) and the X-ray structural data allowed us to obtain the accurate cation site distribution and the Fe 2+ -Mg degree of order. This leads to a closure temperature (Tc) of 500 with a standard deviation of ± 100°C that would correspond to a slow cooling rate, which is in disagreement with petrologic evidence that indicates that this sample originates from a fast cooled (~ 3-6°C/h) lava flow .In order to clarify this discrepancy we undertook (i) a SC-XRD study of an augite (~ En49Fs9 Wo42) from a pyroxenite (TS7) of Theo's flow, a 120-m-thick lava flow regarded as a terrestrial analogue of MIL 03346; (ii) an annealing experiment at 600°C on a crystal from exactly the same fragment of MIL 03346. SC-XRD data from TS7 augite yields a Tc= 600(20)°C, consistent with the cooling rate expected at 85m below the surface. This Tc is higher, although similar within error, to the Tc=500(100)°C obtained for MIL03346; thus suggesting relatively slower cooling for MIL 03346 with respect to TS7. The annealing experiment on the MIL 03346 crystal clearly showed that the degree of order remained unchanged, further confirming that the actual Tc is close to 600°C.This result appears inconsistent with the shallow depth of origin (~ <2m) assumed for MIL 03346, further supporting the discrepancy between MIL 03346 textural and petrologic evidence of fast cooling and the abovementioned Tc results obtained for augite. Therefore, a tentative scenario is that, soon after eruption and initial quench and while still at relatively high-T (~ 600°C), MIL 03346 was blanketed with subsequent lava flows that slowed down the cooling rate and allowed the augite Fe 2+ -Mg exchange reaction to proceed.

Accurate determination of F in minerals is a diffi cult task even when high F concentrations are present. Fluorine usually is determined by means of electron micro-probe analysis (EMPA) standardized on non-silicate-matrix compounds (e.g., fl uorite), and some previous work has revealed the diffi culties in determining F at high concentrations such as found in the humite-group minerals. Moreover, when both single-crystal structure refi nement (SREF) and EMPA are available for the same crystal, the two estimates do not always agree. On the other hand, the secondary ion mass spectrometry (SIMS) technique is not easily applied at high F concentrations due to the existence of matrix effects related to the chemical composition and structure of the sample as well as to the concentration of the element itself. We tested the agreement among these analytical techniques in the estimation of high F contents and propose an analytical procedure for the analysis of fl uorine. Our results indicate that careful selection of working conditions for EMPA of F together with appropriate correction, can yield accurate fl uorine concentrations in minerals. Fluorine data extracted from refi ned site occupancies are systematically overestimated. New accurate working curves have been worked out for SIMS analysis of F taking Si and Mg, in turn, as the reference element for the matrix. Humite-group minerals show SIMS matrix effects on the order of ~10%. In analyzing fl uoborite in the most unfavorable cases, the difference in Ion Yield (F/Mg) between "disoriented" humite-group minerals and "oriented" fl uoborite samples can reach ~27%. Finally, a lower than expected IY(F/Si) from the F/Si working curve (made with humite minerals) is shown by topaz, which can be ascribed to chemical matrix effects, as well as to the covalent-type bonding between F and the major element in the matrix (Al). they possess lower resolving power than TAP (Fialin et al. 1993). With these new refl ectors, multiple-order interferences greater than the second-order are absent (e.g., the third-order PKα peak in apatite). Nevertheless, interferences due to second-order peaks from Mg and Al and fi rst-order L-lines from Fe still survive and constitute a limitation in the determination of fl uorine in minerals rich in Mg, Al, and transition elements (Raudsepp 1995).