Growth bands

Figure 7. age vs. growth band age for three coral sub-samples, all younger than 200 years old (after Edwards 1988 and Edwards et al. 1988). All three points lie on a 1 1 line indicating that the °Th ages are accurate and that initial is negligible, justifying the use of Equation (1) to determine °Th age. 

Baker A, Smart PL, Edwards RL (1996) Mass spectrometric dating of flowstones from Stump Cross Caverns and Lancaster Hole, Yorkshire palaeoclimate imphcations. J Quat Sci 11 107-115 Baker A, Smart PL, Edwards RL Richards DA (1993b) Annual growth banding in a cave stalagmite. Nature 364 518-520... 

The contrast of growth bands, which arise from changes in lattice parameter due to fluctuations in impurity levels, is particularly valuable in determining the growth history of crystals. No contrast is observed when g.n=0, n being a vector normal to the growth front. 

Fatigue resistance increases with the [PU] up to 50Z, while energy absorption determined from dynamic properties and pendulum impact tests varies directly with the [PU], The micromechanism of failure Involves the generation of discontinuous growth bands associated with shear yielding rather than crazing. 

With respect to micromechanisms of failure, at low values of Ak, discontinuous growth bands whose spacings correspond to many cycles of loading were observed (26,32). Figure 10 shows the effect of composition on r, the spacing of the bands, the yield stress o (estimated from the Dugdale relationship, r ifK /80 ), and tlJe... 

Figure 11. Comparison of ra the length of discontinuous growth bands as a function of AKa for PU/PMHA SINs with values for several other polymers (26).

In natural crystals, whose growth processes cannot be directly observed, the difference in R is recorded as the difference in separation in growth banding (see Chapter 6). Based on these observations, several papers were reported in which the direction of flow of ore-forming fluid was evaluated in pegmatite and hydrothermal veins. In many cases in which the natural mineral crystals exhibited extensively malformed Habitus from that predicted by the structural form, the malformation could be considered to be due to the remarkable anisotropy involved in the environmental conditions, such as the directional flow of the solution, which is similar to the situation of growth of NaCl from solution in between two glass plates, as discussed above. 

Figure 6.2. Cathodoluminescence tomograph of an emerald crystal synthesized by the high-temperature solution growth method. Note the regularly spaced faint growth banding appearing in between two distinct bands. (By courtesy of T. Miyata.)...

Figure 6.3. Expected difference in the features of growth banding in respective growth sectors depending on the order of morphological importance (MI, > MI >Ml3).A, B, and C indicate growth sectors corresponding to respective faces and the features to be observed in growth banding. The distribution of dislocations is not indicated.

Growth banding seen in different growth sectors will have different features depending on the order of morphological importance. This is due to environmental conditions. 

Figure 6.3 illustrates schematically features seen in the growth banding patterns in respective growth sectors, in relation to the order of morphological importance of the crystal faces. A rough interface disappears as growth proceeds, but the... 

Internal straight growth banding cutting rounded external form banding pattern with irregular form... 

As discussed above, most natural diamond crystals are characterized by dislocation bundles originating from the center of a crystal and running nearly perpendicularly to the 111 surface with a growth banding pattern parallel to 111. There are, however, crystals showing complicated curved banding patterns, the origin of which will be a subject for future study. 

Knutson, D. W., Buddemeier, R. W., and Smith, S. V. Coral chronometers Seasonal growth bands in reef corals. Science 1 77, 270-272 (1972). 

Because annual growth bands of sufficient size to permit chemical analysis form in corals, considerable effort has gone into the study of incorporation of trace components in these organisms. Experimental studies, such as those by Smith et al. (1979), have contributed substantially to the reliability of the use of the Sr content of corals as a paleothermometer, and the efforts of other researchers (e.g., Buddemeier et al., 1981 Swart and Hubbard, 1982 Shen and Boyle, 1988) have yielded insight into the processes controlling a variety of minor components in corals. 

Figure 27 X-ray topograph (Lang s technique) of a crystal of TEA(TCNQ)Z grown from thin stationary seed by fast cooling (4°C/day) (a) topography image (b) interpretation s is the seed, s, is an internal seed x, inclusions dislocations =, growth bands —, growth section boundary —, suspending fiber. The crystal size is 12 X 5 x 0.3 mm3. (From Ref. 200.)...

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