symmetrical extinction In optical mineralogy, the phenomenon which occurs when the vibration direction of the light bisects the angles between two sets of cleavages (as seen in basal sections of pyroxenes and amphiboles). A special form of symmetrical extinction may also occur in twinned crystals (see CRYSTAL TWINNING) of feldspar, and this may be used to determine their composition.
More From encyclopedia.com
Diastem , diastem A very small break in a conformable succession of strata, indicated only by a bedding plane, and representing a brief interruption in the dep… Chelford , Chelford 1. An interstadial that occurred 65 000–60 000 years BP, during the Devensian glaciation. 2. Sections of alluvial sands and organic muds con… diabase , dolerite (diabase, microgabbro) A dark-coloured, medium-grained igneous rock which contains plagioclase feldspar of labradorite composition and pyrox… spinel , spinel Important group of non-silicate mineral oxides, including the subgroups spinel series, magnetite series, and chromite series. Members of the s… Composite Materials , A composite material (or just composite) is a mixture of two or more materials with properties superior to the materials of which it is made. Many co… Polarization Of Light , plane-polarized light (PPL) As light travels, it normally vibrates in all directions at right angles to the line of transmission. If a strongly absor…
About this article
Updated About encyclopedia.com content Print Article
You Might Also Like