Search results
Results from the WOW.Com Content Network
The mineral usually has polysynthetic twins, which are only visible in thin sections when the specimen is inspected under polarized analyzed light. [4] Analcime mainly consists of oxygen (50.87%), silicon (25.51%), aluminum (12.26%), sodium (10.44%) but otherwise has a negligible amount of hydrogen (0.92%) as well. [5]
Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or "record-groove" effect. Plagioclase is a major constituent mineral in Earth's crust and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks.
Twinning results when different parts of the crystal break their isometric symmetry along a different choice of axis. This is typically polysynthetic twinning, which enables the crystal to maintain its isometric shape by averaging out the displacement in each direction. This produces a pseudomorphic crystal that appears to have isometric symmetry.
Ulexite displays polysynthetic twinning parallel to the elongation, along {010} and {100} (Murdoch, 1940). [11] In thin sections cut parallel to the fibers, ulexite grains display both length-fast and length-slow orientations in equal quantities because the intermediate axis (y) of the indicatrix is roughly parallel to the elongation of the ...
As a rule, belomorite forms solid granular and crystalline masses or massive crystalline aggregates; crystals of tabular and tabular-prismatic types are much less common. Complex polysynthetic twinning is very often observed.
Green to dark green; colorless to pale green in thin section: Crystal habit: Rarely in rough crystals; anhedral, granular to massive: Twinning: Single and polysynthetic twinning common on {100} Cleavage: Good on {110}, {110} ^ {1 1 0} ≈87°; parting on {100} Fracture: Uneven to conchoidal: Tenacity: Brittle: Mohs scale hardness: 5–6: Luster ...
Kourtney called the fetal surgery “terrifying,” and her fear was compounded with her husband, Travis, 48, not being able to be by her side. Travis Barker and Kourtney Kardashian. Courtesy of Hulu
This combination leads to a grid pattern, hence microcline displays gridiron twinning. Can also display carlsbad twinning, simple twins, or lack twinning altogether. Lamellae in microcline are discontinuous and "pinch and swell". Photomicrograph of thin section of microcline showing crosshatched crystal twinning (in cross polarized light) Cleavage