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Schlieren "flames" |
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| Meteorite, Ysleta, Iron, ungrouped. |
| "Schlieren" is German for stria or streak, from earlier
Middle High German "slier". It's a "broad-brush" term used
in several science disciplines and can be found in publications on geology,
petrography, optics, chemistry, metallurgy, meteoritics, fluid dynamics, and
the study of biological processes. Although its use seems to vary within these disciplines, one common use is to define lines and shapes. For this page, schlieren flames are defined as irregular streaks or masses that differ transitionally from surrounding composition or textures. Ysleta, Iron, ungrouped. Texas, USA Buchwald, 1975, describes Ysleta as polycrystalline with a plessitic matrix. Polished sections show no obvious macrostructure. However, a light etching shows many parent austenite grains, each 1-2 cm in a coarsely-defined diameter. When the higher temperature austenite in Ysleta started its transformation to kamacite, nucleation began on the grain boundaries. These boundaries have been described (Buchwald) as "delicate and only visible as 10-50-micron wide kamacite veins". Cooling later transformed the austenite into micron-sized plessitic mixtures of alpha-iron and gamma-iron, and within millimeter-sized regions, "schlieren flames" can be seen. In this instance, the schlieren are not lines. They are shapes, "flame shapes". |
Figure 1. Scale bar 600 µm. |
| Ysleta, Iron, ungrouped. |
| Flame shaped structures (primary, forming during nucleation of austenite to kamacite). The flame shapes occur within millimeter-sized, fine grained duplex mixtures (populations) of alpha-iron and gamma-iron. |
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