Effect of Transition Elements upon the Nucleation and the Morphology of Magnetite in Silicate Melts of Basaltic Composition

Effects of transition elements, Ti, Cr and Cu upon the nucleation and morphology of mag-netite in silicate melts of basaltic compositon were examined. Crystallization of magnetite was carried out at △T= — 10°C in the atmospheric condition. Quenched products are composed of magnetite, (plagi-oclase) and silicate glass. Examinations of the morphology of magnetite show that an addition of Ti and Cu with Keff 1, has a definite effect to decrease grain size and to increase the number of crystals. The results obtained were discussed in relation to σ*, σ** and Keff

Fasciation in Strawberry Floral Organs and Possible Implications for Floral Transition

Fasciation in strawberry is characterized by an enlarged and flattened receptacle, clustering of flowers, and altered inflorescence architecture. However, the developmental process of fasciated flowers remains obscure. In this study, the fasciation incidence and developmental process in the primary fruit and inflorescence architecture were evaluated and compared for the non-susceptible cultivars, ‘Nyoho’ and ‘Sagahonoka’ and one of the most susceptible cultivars, ‘Ai-Berry’. The severity and frequency of flower and inflorescence fasciation was clearly greater in the vigorously growing large plants of ‘Ai-Berry’ compared to small plants and large plants of the other two cultivars. In ‘Ai-Berry’, the deformation of the large shoot apical meristem (SAM) into an oval shape was the initial symptom observed before and during floral transition. Such oval-shaped SAMs often differentiated two or more leaf primordia almost at the same time, which then developed into divided multiple vegetative SAMs before floral transition and linearly-fasciated SAMs during floral transition, respectively. The development of fasciation symptoms was observed after downregulation of FaTFL1. Although inflorescence or receptacle fasciation could be controlled when early and rapid floral induction was achieved by intermittent low-temperature treatment, severe fasciation was observed in late-flowered plants which were either not responsive or not subjected to this treatment. These results indicate that fasciation of floral organs may be triggered and develop during floral transition and that temperature fluctuations around boundary values between floral inhibition to induction may cause a half-finished or slowly processed floral transition and finally result in severe fasciation in vigorously growing ‘Ai-Berry’ plants

Characteristics of crystal growth in nature as seen from the morphology of mineral crystals

Crystal growth from solution phases is most universal and important in natural crystallization. Its essential features are : 1) mass transfer and 2) interaction between solid and liquid phases, in addition to lower growth temperatures, and, in general, smoother solid-liquid interfaces, as compared to melt growth. The morphology of crystals changes depending on the degree of supersaturation σ in solution growth, and there are two transitional supersaturations σ* and σ**, where transitions from bulky to hopper, and from hopper to dendritic morphologies occur, respectively. Changes of morphology during crystal growth (internal morphology) may be analysed on this basis. The σ* and σ** vary depending on materials and environmental conditions. Surface microtopographies of crystal faces of natural crystals are analysed using a-factors and γ, Δμ/kT, and compared with laboratorically synthesized crystals, and characteristics of natural crystallization are discussed. Growth under metamorphic and metasomatic conditions are also analysed based on the surface microtopographic observations.La croissance cristalline en solution est le plus universel et le plus important des processus de cristallisation naturelle. Ses traits essentiels sont : 1) le transfert de masse et 2) l'interaction entre phases solide et liquide, en plus des températures de croissance plus basses et des interfaces solide-liquide plus lisses que dans la croissance en fusion. La morphologie des cristaux diffère suivant le degré de sursaturation a dans la croissance en solution, et il existe deux valeurs de sursaturation de transition σ* et σ**, où s'effectuent des transitions respectivement de morphologie massive à morphologie en trémie et de morphologie en trémie à morphologie dendritique. On peut analyser sur cette base, les changements de morphologie pendant la croissance cristalline (morphologie interne). Les valeurs σ* et σ** varient suivant les matériaux et les conditions environnantes. On analyse des microtopographies en surface de faces cristallines de cristaux naturels, en utilisant les facteurs-α ainsi que γ, Δμ/kT, et on compare avec des cristaux synthétisés en laboratoire ; on discute les caractéristiques de la cristallisation naturelle. On analyse aussi la croissance dans les conditions métamorphique et métasomatique en se fondant sur l'observation de microtopographies en surface.Sunagawa Ichiro. Characteristics of crystal growth in nature as seen from the morphology of mineral crystals. In: Bulletin de Minéralogie, volume 104, 2-3, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Première partie : croissance cristalline / Physique des minéraux / Microscopie électronique

Natural and synthetic gem materials, a comparison

Properties of crystalline materials may vary to a considerable extent depending on their growth histories and growth conditions. This fact forms the basis on which a distinction between natural and synthetic gem materials is made. The differences do not appear on an atomic or a lattice scale, but can be detected on a larger scale in which changes occurred during growth processes are reflected. The latter includes external morphology of crystals, surface microtopography of crystal faces, growth bandings, sector structures, inclusions, dislocations, planar defects, like stacking faults and micro-twins, etc. Since growth mechanisms are different among crystals grown from different phases, and the environmental conditions are different among crystals grown from similar phases, the differences between natural and synthetic gem materials of different origins will be visualized if appropriate methods of detection are applied. To demonstrate this, lattice images of natural and synthetic emeralds, X-ray topography and surface microtopography of natural and synthetic diamonds and emeralds are compared.Les propriétés des matériaux cristallisés peuvent varier d'une manière considérable en fonction de leurs histoires et conditions de croissance. Ceci est à l'origine de la distinction entre matériaux gemmes naturels et synthétiques. Ces différences n'apparaissent pas à l'échelle atomique ou à celle du réseau, mais se manifestent à plus grande échelle lors de modifications des processus de croissance. Ces différences touchent la morphologie externe des cristaux, la microtopographie des faces cristallines, les zones de croissance, la sectorisation, les inclusions, les dislocations, etc. Les mécanismes de croissance étant différents pour des cristaux crûs à partir de phases dissemblables et aussi pour des cristaux obtenus à partir de phases semblables mais dans des conditions différentes, les distinctions entre matériaux gemmes naturels et synthétiques d'origines variées seront visualisées si des méthodes de détection appropriées sont utilisées. Afin de démontrer ceci, des images de réseau d'émeraudes naturelles et synthétiques, la topographie aux rayons X et la microtopographie de surface de diamants et émeraudes naturelles et synthétiques sont discutées à fins de comparaisons.Sunagawa Ichiro. Natural and synthetic gem materials, a comparison. In: Bulletin de Minéralogie, volume 104, 2-3, 1981. 12e assemblée générale de l'I.M.A. - Orléans – Juillet 1980. Première partie : croissance cristalline / Physique des minéraux / Microscopie électronique

Chemical compositions of chondrules and matrices in the ALH-77015 chondrite (L3)

The chondrules and matrices in ALH-77015 chondrite (L3) were analyzed with an electron probe microanalyzer. The matrices are relatively homogeneous, whereas the chondrules show a wide compositional variation. There is a clear compositional gap between the matrices and the chondrules and between olivines in the chondrules and those in the matrix. Fragmentation of chondrules cannot explain the chemistry of the matrices. A clear correlation between Ca and Al has been noted in the chondrules. The correlation can be interpreted by assuming that the chondrules were formed from the solar nebula through the crystallization of anorthite and Ca-rich pyroxene

Ferropseudobrookite-silica mineral-albite-chondrule in the ALH-77015 chondrite (L3)

Ferropseudobrookite-silica mineral-albite-chondrule was found in an unequilibraed (L3) chondrite (ALH-77015). This is the first finding of ferropseudobrookite in chondrite. The ferropseudobrookite exhibits a weakly zonal structure. The stability field of ferropseudobrookite suggests that the chondrule should have been quenched at a temperature near 1140±10℃