New insight into the pectolite – serandite series: a single crystal diffraction study of Na(Ca_1.73Mn_0.27)[HSi₃O₉] at 293 and 100 K

Abstract

Using synchrotron radiation, a single crystal investigation has been performed at 293 and 100 K for the structural characterization of the manganoan pectolite, Na(Ca

The incommensurately modulated structures of natural natrite at 120 and 293 K from synchrotron X-ray data

“…in the Khibiny alkaline massif (Mt. Koashva) and then donated to the Musée cantonal de géologie of Lausanne, and consists of natrite, partially altered on the surface to trona and thermonatrite and contains inclusions of dark-brown lamellae of lomonosovite, Na 2 Ti 2 Si 2 O 9 Na 3 PO 4 , olive-green prisms of aegirine, NaFeSi 2 O 6 , and colorless bright prisms of manganoan pectolite, Na(Ca 1.73 Mn 0.27 ) [HSi 3 O 9 ] previously studied by Arakcheeva et al (2007). Both samples are housed in the collection of the Musée cantonal de géologie of Lausanne (catalog numbers: MGL 58960 and MGL 92266 for Lv and Kh, respectively).…”

A variable-temperature neutron diffraction study of serandite: A Mn-silicate framework with a very strong, two-proton site, hydrogen bond

“…The resulting model, with refined hydrogen atom positions and occupancies, yielded lower R-values, suggesting an improvement over the previous one-proton site system. A synchrotron SXD experiment by Arakcheeva et al (2007) investigated the structural variations of minerals in the serandite-pectolite series at both 100 and 293 K. This study of the manganoan pectolite, Na(Ca 1.73 Mn 0.27 )[Si 3 O 8 (OH)], did not investigate the two-proton site model, presumably due to the limitations of X-ray diffraction compared with neutron diffraction in locating hydrogen atoms. It did, however, indicate the strengthening of the hydrogen bond with decreasing temperature, with the hydrogen atom moving to a more symmetric position between O3 and O4.…”

Marshallsussmanite, NaCaMnSi3O8(OH), a new pectolite-group mineral providing insight into hydrogen bonding in pyroxenoids

“…Strong hydrogen bonding within the pectolite group has received much study (Prewitt, 1967;Takéuchi et al, 1976;Takéuchi and Kudoh, 1977;Jacobsen et al, 2000;Arakcheeva et al, 2007;Williams and Weller, 2014). Prewitt (1967) noted the proximity of non-bridging O atoms in the silicate chain of pectolite, estimating an O3•••O4 separation of only 2.482 Å.…”

“…In the structure of serandite, Takéuchi et al (1976) found a yet shorter O3•••O4 separation of 2.453 Å. Prewitt (1967) and Arakcheeva et al (2007) both located H closer to O3 than O4 in pectolite, indicating an asymmetric H bond. Using single-crystal neutron diffraction on serandite, Jacobsen et al (2000) found an irregular feature in the difference map, which they modelled as two separate H positions.…”