Enstatite MgSiO

Emission and excitation spectra and luminescence decay curves of enstatite single crystals nominally doped with Ni and Cr have been measured at temperatures down to 10 K. For all the crystals under investigation, the emission band peaking at about 1520 nm was assigned to the T2- A2 transition of octahedral Ni center, while the luminescence around 800 nm was assigned to the T2- A2 transition of octahedral Cr centers (Moncorge et al. 1999). 

Natural iron free enstatite exhibits mainly two orange-red luminescence bands peaking at 660 and 590 nm ascribed to Mn centers substituting for Mg in different structural positions (Gorobets and Rogojine 2001). Luminescence bands peaking at 620-628 nm range have been found under 532 nm laser excitation (http //miff.info) (Fig. 4.174). 

The luminescence spectra of Cr centers in two chlorite crystals (Fig. 4.176) have been presented (Czaja et al. 2014). Chromium ions occupy the strong crystal-field site M4 in the brucite sheet and the intermediate crystal-field site in the inner 

Under cw laser excitation the structured emission spectrum appear (Fig. 4.177) 

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Si04 units share two corners to form infinite chains (Figure 1.52(c)). The repeat unit is SiOs . Minerals with this structure are called pyroxenes (e.g., diopside (CaMg(S 103)2) and enstatite (MgSiOs)). The silicate chains lie parallel to one another and are linked together by the cations that lie between them. 

We can estimate how much water was dissociated by considering the oxidation of the mantle. If the Earth started out with the oxidation state of chondrites (although not necessarily of total chondritic composition), it would take the oxygen from about one present-day ocean volume to reach the oxidation state of the mantle inferred from mantle-derived rocks. Alternatively, if we start with a more reduced ensemble, suggested by condensation calculations from a solar nebula, we will have primarily enstatite (MgSiOs) and metallic iron as the original source to be oxidized. The oxidation reaction would then be as shown in eqn [1]. 

If we proceed further in the direction towards the atomic linkage corner of the tetrahedron, we come to lattices which cohere in two directions by ionic forces but in one by atomic forces they belong to a definite group of silicates whose structure will be discussed later in another connection (see p. 169). Particularly well known representatives are enstatite MgSiOs, diopside CaMg (8103)2 and asbestos. The latter at once suggest by their very marked fibrous habit that in one direction a particularly strong link prevails, namely, the atomic it is produced in the lattice by O-Si-0 chains, while in the other two directions weaker ionic forces prevail. 

Talc loses its water of hydration at 1000°C. At this temperature, the talc crystal restructures itself to form the mineral enstatite (MgSiOs), which is significantly harder than talc, with a Mohs hardness of 5-6, and less platy. Talc is inert to most chemicals. It normally will absorb an equilibrium 0.2-0.3% by weight of moisture under normal atmospheric conditions. 

SijO - Metasilicates Enstatite MgSiO, Beryl Be3Al2(Si03)g... 

Schrqrer, 1965). At high temperatures, such as 980 C, an additional crystal phase develops. This crystal phase has been identified as enstatite, MgSiO. ... 

Plate 7 Pyroxene Crystal. 7a 2010 Augite-La Panchita Mine, Mun de La Pe, Oaxaca, Mexico by Rock Currier. 7b 2010 Enstatite-83152 by Rob Lavinsky. 7c 2011 Diopside Aosle by Didier Descouens. Pyroxene is Ca-Mg-Fe silicate ((Ca, Mg, Fe) Si03) and classified as augite (Ca, Mg, Fe) Si20s (Plate 2A), enstatite (MgSiOs) (Plate 2B), diopside (CaMgSi20s, (Plate 2C). It occurs in volcanic rocks (basalt, andesite) and skam-type deposits (see Chap. 1)... 

Figure 8.14a, b shows the XRD of coupled glasses with TBV and YSZ electrolytes, respectively indicating no phase formation even after 100 h heat treatment. After 750 h heat treatment at 800°C, coupled TBV showed pyrochlore (La2Si207) and enstatite (MgSiOs) phase formation which may follow the reactions kinetics as... 

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