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Crystal twinning occurs when two or more adjacent crystals of the same mineral are oriented so that they share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals that are tightly bonded to each other.
Crystal structure of cassiterite. Crystal twinning is common in cassiterite and most aggregate specimens show crystal twins. The typical twin is bent at a near-60-degree angle, forming an "elbow twin". Botryoidal or reniform cassiterite is called wood tin. Cassiterite is also used as a gemstone and collector specimens when quality crystals are ...
Variously described as a "screaming" or "crackling" sound, the effect is caused by the crystal twinning in the metal. [1] The sound is not particularly loud, despite terms like "crying" and "screaming". It is very noticeable when a hot-dip tin coated sheet metal is bent at high speed over rollers during processing.
In handsamples, macroscopically visible staurolite crystals are of prismatic shape. The mineral often forms porphyroblasts. In thin sections staurolite is commonly twinned and shows lower first order birefringence similar to quartz, with the twinning displaying optical continuity.
Crystal habit: Can be anhedral or euhedral. Grains are commonly elongate with a tabular appearance. May contain lamellae which formed from exsolved albite. Twinning: Typically displays albite twinning and pericline twinning. This combination leads to a grid pattern, hence microcline displays gridiron twinning.
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.
The doctors and nurses didn’t believe Tomisa Starr was having trouble breathing. Two years ago, Starr, 61, of Sacramento, California, was in the hospital for a spike in her blood pressure.
Pericline is a form of albite exhibiting elongate prismatic crystals. [1] Pericline twinning is a type of crystal twinning which show fine parallel twin laminae typically found in the alkali feldspars microcline. [2] The twinning results from a structural transformation between high temperature and low temperature forms. [3]