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Gneiss with large eye-shaped feldspars. Augen (from German "eyes") are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye. [1] Feldspar, quartz, and garnet are common minerals which form augen. [2]
Augen gneiss, from the German: Augen, meaning "eyes", is a gneiss resulting from metamorphism of granite, which contains characteristic elliptic or lenticular shear-bound grains (porphyroclasts), normally feldspar, surrounded by finer grained material. The finer grained material deforms around the more resistant feldspar grains to produce this ...
The streaked-augen gneiss member consists of uniform, medium-grained biotite-microcline-quartz-plagioclase gneiss, with augen that have a "stretched" or "streaked" appearance. [1] The hornblende gneiss member is similar to the layered gneiss member, but with hornblende-bearing dark gneiss accounting for about half of the outcrop area. [1]
In some of the Blue Ridge Mountains occurrences, an epidotized augen gneiss is present exhibiting foliation structures. The dominant green epidote in unakite rocks is the metasomatic alteration product of plagioclase feldspar, while the orthoclase and quartz crystals remain unaffected.
Gneiss, a foliated metamorphic rock. Quartzite, a non-foliated metamorphic rock. Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [1] The word comes from the Latin folium, meaning "leaf", and refers to the sheet-like planar structure. [1]
"Books" for OT or NT, as in Old Testament or New Testament. "Sailor" for AB, abbreviation of able seaman. "Take" for R, abbreviation of the Latin word recipe, meaning "take". Most abbreviations can be found in the Chambers Dictionary as this is the dictionary primarily used by crossword
However, for certainty, other distinguishing features of quartz include the fact that it is uniaxial, it has a positive optic sign, length-slow sign of elongation, and zero degree extinction angle. [5] A sigma clast as seen in an ultra thin section. The uneven coloring is an artifact from uneven polishing.
The gneiss of the Higher Himalayan zone (HHZ) is a thick continuous sequence of about 5 to 15 km. [23] The northern part is marked by the North Himalayan Normal Fault (NHNF), which is also known as the South Tibetan Detachment system (STDS). At its base, it is bounded by the MCT.