Idiomorphic crystals

Shortbort VIII bort, aggregate of idiomorphic crystals... 

In volcanic rocks formed by the solidification of magma near the Earth s surface, small cavities of millimeter to centimeter order are often present, in which idiomorphic crystals of phlogopite and hematite occur. All these crystals grown from the vapor phase show typical spiral patterns. However, they grow in a much-reduced free space as compared to the case of pegmatite, and this characteristic is well represented on their surface microtopographs. 

The core portion consists of an idiomorphic crystal of a single phase, either emerald, ruby, or sapphire. 

Despite the simplicity of the method there are three reasons why thermal dehydration recipes are not given here (1) Hematite produced in this way does not consist of idiomorphic crystals at temperatures of up to ca. 500-600 °C pseudomorphs of the precursor result and above 600 °C coalesced crystals with ill-defined crystal faces are obtained and the surface area is low, (2) In natural environments hematite rarely forms at such high temperatures, and (3) natural hematites frequently consist of single, more or less idiomorphic crystals. 

Idiomorphic crystals are crystals whose crystal habit is determined by internal structure. 

In methods 1-3 of section 10.2, parameters such as type of anion, acidity and [Fe] are varied to give monodispersed hematites with idiomorphic crystals of different sizes and shapes. 

Morphologies of synthetic hematite include plates and discs, rods, spindles, spheres, ellipsoids, double ellipsoids, rhombohedra, stars, cubes and peanuts. In the absence of additives, hexagonal plates, which are often rounded, and rhombohedra predominate. Each morphology can be obtained by more than one synthesis route. Two common ways of producing idiomorphic hematite crystals in aqueous systems... 

Fig. 98. Distribution of components in interbedded schist (clastic) and cherty iron (chemogenic) layers a = schists with disseminated idiomorphic magnetite crystals (porphyroblasts) h = somewhat sideritic bands figures = sample numbers. For symbols, see Fig. 97.

Linear thin y layer next to the steel with a narrow layer of coherent 8 phase, above which is a region of fragmented 8 in a zinc matrix interspersed above this are large isolated crystals of pronounced idiomorphic habit (e.g., silicon). 

Evenly distributed phases idiomorphic alite rounded belite finely differentiated matrix scarce, small, free-lime crystals Optimized manufacturing conditions correcf chemical composition of raw feed, well mixed, no particles too coarse, satisfactory maintenance of sintering and cooling temperatures (Hofmanner, 1973)... 

Large to very large, idiomorphic alite crystals Correlated with increasing SO3 content in low-alkali laboratory clinkers reduced viscosity of melt strength loss (Dreizier, Strunge, and Knofel, 1985)... 

Mordenite are also depicted in Fig. 2.6i. Clinoptilolite has been reported to occur as idiomorphic plates and laths, which are several micrometers in length and 1-2 pm in thickness, whereas, most of the crystals display characteristic monoclinic symmetry and many are cofhn-shaped. Some zeolites appear as fibrous aggregates as depicted in Fig. 2.6i, whereas, others as robust, non-fibrous crystals as seen in Fig. 2.6b, d, h, m, n [8, 34, 42, 54, 56, 57]. 

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