Ma Zhesheng

Crystal structure refinement of suolunite and its significance to the cement techniques

Based on the crystal structure refinement, the arrangement and characteristics of the double tetrahedra of Si-O backbone of suolunite have been precisely clarified. The double tetrahedra are isolated, and the orientations of the closely adjacent double tetrahedra are perpendicular to each other, which results in the poor cleavage and high hardness of suolunite. Compared with the crystal structure of synthesized C-S-H minerals in Portland cement hydrates, this mineral apparently avails the increasing of the compressive strength of cement materials and the manufaturing of high performance concrete. Thus this research provides a new idea for the optimization of Portland cement manufaturing techniques.Based on the crystal structure refinement, the arrangement and characteristics of the double tetrahedra of Si-O backbone of suolunite have been precisely clarified. The double tetrahedra are isolated, and the orientations of the closely adjacent double tetrahedra are perpendicular to each other, which results in the poor cleavage and high hardness of suolunite. Compared with the crystal structure of synthesized C-S-H minerals in Portland cement hydrates, this mineral apparently avails the increasing of the compressive strength of cement materials and the manufaturing of high performance concrete. Thus this research provides a new idea for the optimization of Portland cement manufaturing techniques.

Titanium, Ti, A New Mineral Species from Luobusha, Tibet, China

: We describe the new mineral species titanium, ideally Ti, found in the podiform chromitites of the Luobusha ophiolite in Tibet, Peoples Republic of China. The irregular crystals range from 0.1 to 0.6 mm in diameter and form an intergrowth with coesite and kyanite. Titanium is silver grey in colour, the luster is metallic, it is opaque, the streak is grayish black, and it is non-fluorescent. The mineral is malleable, has a rough to hackly fracture and has no apparent cleavage. The estimated Mohs hardness is 4, and the calculated density is 4.503 g/cm3. The composition is Ti 99.23–100.00 wt%. The mineral is hexagonal, space group P63/mmc. Unit-cell parameters are a 2.950 (2) A, c 4.686 (1) A, V 35.32 (5) A3, Z= 2. The five strongest powder diffraction lines [d in A (hkl) (I/I0)] are: 2.569 (010) (32), 2.254(011) (100), 1.730 (012) (16), 1.478 (110) (21), and 0.9464 (121) (8). The species and name were approved by the CNMNC (IMA 2010-044).

Tangdanite, a new mineral species from the Yunnan Province, China and the discreditation of ‘clinotyrolite’

Abstract Tangdanite, ideally Ca2Cu9(AsO4)4(SO4)0.5(OH)9·9H2O and monoclinic, is a new mineral species (IMA No. 2011-096) occurring in the Tangdan and Nanniping mines, southeast Dongchuan copper mining district, Dongchuan County, Kunming City Prefecture, Yunnan Province, P. R. China (26°11’N 103°51’E). The mineral is found in the oxidized zone (gossan) of an As-bearing Cu sulfide deposit and is clearly of supergene origin. Associated minerals are chalcopyrite, bornite, chalcocite, covellite, tennantite, enargite, cuprite, malachite, azurite, copper and brochantite. Crystals form radiating or foliated aggregates of flaky crystals up to 3 mm, flattened parallel to (100) and elongated along [001]. It is emerald green with a light green streak, translucent and has a pearly to silky lustre. It is sectile having perfect cleavage on {100} although neither parting nor fracture was observed. No fluorescence in long- or short-wave ultraviolet radiation was observed. The hardness is VHN50 42.0-43.6, mean 42.8 kg mm-2 (2-2 ½ on the Mohs scale). The density measured by pycnometry is 3.22 g cm-3 (Ma et al., 1980). The calculated density from the empirical chemical formula is 3.32 g cm-3. The compatability index gives 1 - (Kp/Kc) = -0.041 (good). The empirical formula (based on 36 O a.p.f.u) of tangdanite is Ca2.05Cu9.08(As1.03O4)4(S0.63O4)0.5(OH)9·9H2.04O. The simplified formula is Ca2Cu9(AsO4)4(SO4)0.5(OH)9·9H2O. The strongest five reflections in the X-ray powder-diffraction pattern [d in Å (I) (hkl)] are: 4.782(100) (3̄ 1 1), 4.333(71) (6 0 2), 5.263(54) (2̄ 0 2), 3.949(47) (8 0 2) and 2.976(46) (15̅ 1 1). The unit-cell parameters are a = 54.490(9), b = 5.5685(9), c = 10.4690(17) Å, b = 96.294(3)°, V = 3157.4(9) Å3, Z = 4. Its structure was solved and refined in space group C2/c, with R = 0.110.

Quadrupole splitting distributions in triclinic astrophyllite

The mineral, triclinic astrophyllite, was investigated using the Mossbauer effect. The Mossbauer spectra of triclinic astrophyllite at 298 K, 180 K and 90 K were measured, and the quadrupole splitting distributions (QSDs) from the Mossbauer spectra were obtained by using a Voigt-based method for line shape analysis. The distortion parameters, the variances of the octahedral bond angles for triclinic astrophyllite, were calculated, and a site assignment was tentatively given based on the distortion parameters. According to the ratios of ferric to total iron obtained by the Mossbauer effect and the mean value of f (Fe 3+ (O))/ f (Fe 2+ (O)), the chemical formula of triclinic astrophyllite was rewritten.