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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.
Orthoclase crystal twinning from the Organ Mountains in New Mexico. Orthoclase is a common constituent of most granites and other felsic igneous rocks and often forms huge crystals and masses in pegmatite. Typically, the pure potassium endmember of orthoclase forms a solid solution with albite, the sodium endmember (NaAlSi 3 O 8), of plagioclase.
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
For more than 50 years, a spinal fusion has been to the go-to surgery for herniated discs. But a new procedure may offer an alternative. New back surgery gaining popularity to alleviate pain [Video]
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.
An ordinary 30 μm thin section is prepared as described above but the slice of rock is attached to the glass slide using a soluble cement such as Canada balsam (soluble in ethanol) to allow both sides to be worked on. The section is then polished on both sides using a fine diamond paste until it has a thickness in the range of 2–12 μm.
Video-assisted thoracoscopic surgery (VATS) is a type of minimally invasive thoracic surgery performed using a small video camera mounted to a fiberoptic thoracoscope (either 5 mm or 10 mm caliber), with or without angulated visualization, which allows the surgeon to see inside the chest by viewing the video images relayed onto a television screen, and perform procedures using elongated ...
Tommy John, for whom the surgery is named, in 2008. At the time of John's operation, Jobe estimated the chance for success of the operation at one in 100. [18] By 2009, the odds of complete recovery had risen to 85–92%. [19] Following his 1974 surgery, John missed the entire 1975 season rehabilitating his arm before returning for the 1976 season.