Rosette aggregates

Fig. 38.—Various forms of calcium oxalate crystals. A, styloids from the bark of QuiUaja saponaria B, rosette aggregate from rhizome of Rheum officinale C, raphide from the bulb of Urginea maritima D. crystal fiber as seen in longitudinal section in either the xylem or phloem regions of Glycyrrhiza E, microcrystals (crystal sand) isolated from the parenchyma of Belladonna root F, monoclinic prisms and G, twin-crystals from leaves of Hyoscyamus niger. All highly magnified.

Rosette Aggregates—Althaea, Gossypii Cortex, Stramonium, Granatum, Rheum, Fceniculum, Viburnum. 

Rosette aggregates consist of numerous small prisms or pyramids, or hemihedral crystals arranged around a central axis, appearing like a rosette or star. 

Crystal fibers are longitudinal rows of superimposed parenchyma cells each of which contains a single monoclinic prism or rosette aggregate. Crystal fibers are found adjacent to sclerenchyma fibers such as bast or woody fibers. 

Structure of Stem.—Cortex composed of collenchyma and, in the larger stems, of numerous strands of more or less lignified bastfibers strongly lignified wood with medullary rays 1-cell wide pith, often hollow rosette aggregates of calcium oxalate numerous. 

Scalenohedral precipitated calcium carbonate 95-98 1.0-3.5 Steep/ neirrow 5-14 Clustered rosette aggregates, low aspect ratio... 

Fig. 7. Formation of a supramolecular aggregate composed of a compound containing nine melamine rings (the three-layered nonamelamine derivative A) and nine molecules of neohexylisocyanurate (B). Of the 16 possible conformers that can result, two are shown The first has the nine molecules of B arranged in three rosettes of three molecules each, stacked atop each other in the second, the rosettes are staggered with respect to each other such that the rosettes in the first and third layers of A are aligned with each other, but not with the rosette in the second layer. The supramolecular assembly is stabilized...

This species has been used as precursor of nanogold particles by electrodeposition. When the electrodeposition is induced from the isotropic state at 117 °C, the nanoparticles obtained are nanodots aggregated in a spherical-like shape. In contrast, the morphology of the nano particles prepared from the SmA mesophase at 111 °C consist of leaf-like forms interlocked in rosettes. 

The plastic deformation patterns can be revealed by etch-pit and/or X-ray scattering studies of indentations in crystals. These show that the deformation around indentations (in crystals) consists of heterogeneous rosettes which are qualitatively different from the homogeneous deformation fields expected from the deformation of a continuum (Chaudhri, 2004). This is, of course, because plastic deformation itself is (a) an atomically heterogeneous process mediated by the motion of dislocations and (b) mesoscopically heterogeneous because dislocation motion occurs in bands of plastic shear (Figure 2.2). In other words, plastic deformation is discontinuous at not one, but two, levels of the states of aggregation in solids. It is by no means continuous. And, it is by no means time independent it is a flow process. 

In addition to the main types described in Table 2, crystals may form treelike patterns known as dendrites, with such aggregates being termed dendritic or arboraceous. If an aggregate is composed of tiny crystals radiating from a center, it is termed a spherulite or rosette. 

Alternatively, a fiber can be one member of a group or aggregate, as a fibril is one part of a fiber. Spherulites (Fig. 1. IH), fan-shaped fibrous crusts or rosettes, and the veins depicted in Fig. 1.1A are examples of aggregates created when many crystalline fibers grow in close proximity. During fibrous growth, lateral interference may produce planar but irregular bound-... 

As might be anticipated for minerals with chain structures, pyroxenes commonly occur in columnar, prismatic, rodlike, and acicular forms. Enstatite has been found in the form of rosettes of fine-fibrous crystals. Special names such as victorite, chladnite, and shepardite were assigned to different occurrences in this distinctive morphology, possibly because the fibrous aggregates were located in iron meteorites. However, the composition and crystal... 

Fig. 15.3 Aggregates of authigenic hematite rosettes from a Triassic sandstone of the Moenkopi Formation near Gateway, Colorado, USA (Walker et al., 1981, with permission courtesy T. R. Walker).

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