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KIC004406 - euhedral subhedral anhedral eguant crystal...

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Unformatted text preview: euhedral subhedral anhedral eguant crystal habit embayed corroded, resorbed skeletal dendritic curved, branching, parallel crystals host guest graphic intergrowth- micrographic granophyric myrmekitic perthitic antiperthite exsolution epitaxial FORMS QE_INDIVIDUAL GRAINS completely bounded by its characteristic crystal faces (= idiomorphic) crystal faces are only partially developed (=subidiomorphic) crystal faces are completely absent (=xenomorphic) crystal that has approximately the same diameter in every direction external shape (pattern of growth) of a crystal; includes tabular, bladed, lath—shaped, prismatic, acicular, fibrous, micaceous, etc. general term for grains showing rounded corners and embayments; it does not imply a reaction relationShip with the groundmass subhedral or anhedral forms produced by reaction between the crystal and its host liquid crystals which grew or have been corroded to an open frame— work which contains a high proportion of internal voids; may indicate rapid growth and/or quenching a regular branching of fibrous or needle—like crystals shar- ing a common optical orientation - a form of skeletal crystal elongate crystals or mineral grains showing optical continuity or gradational change of optical orientation RELATIONSHIPS BETWEEN GRAINS a large grain containing finer—grained inclusions of another mineral the smaller grain which is included in the host intergrowth in which the guest occurs as angular wedgeushaped forms in the host, resembles cuneiform writing » graphic texture which is visible only under a microscope a texture in which the interstitial or groundmass minerals (usually quartz and alkali feldspar) are intergrown as feath- ery, acicular, or wormy intergrowths;'resembles micrographic but is more irregular a secondary texture in plutonic rocks which consists of ir— regular wormy blebs, rods, or stringers of quartz in sodic plagioclase; usually forms adjacent to alkali feldspar grains irregular veins, patches, lenses, etc of sodic plagioclase in an alkali feldspar host; forms as a result of exsolution similar to perthite but consists of exsolved alkali feldspar in a plagioclase host a solid state reaction in which one phase unmixes into two as the temperature drops (usually); may produce exsolution lamellae (if the guest phase is exsolved preferentially along certain crystallographic planes) or exsolution blebs refers to crystallographically—oriented nucleation of one crystal on another of a different mineral ...
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