Search results
Results From The WOW.Com Content Network
The opposite is anhedral (also known as xenomorphic or allotriomorphic), which describes rock with a microstructure composed of mineral grains that have no well-formed crystal faces or cross-section shape in thin section. Anhedral crystal growth occurs in a competitive environment with no free space for the formation of crystal faces.
Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces (also called facets ) of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal : they are planes of relatively low Miller index . [ 10 ]
Anhedral may refer to: Anhedral angle , the downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft Anhedral (petrology) , a rock texture without crystal faces or cross-section shape in thin section
Crystal shape is also an important factor in the texture of an igneous rock. Crystals may be euhedral, subeuhedral or anhedral: Euhedral or automorphic, if the crystallographic shape is preserved. Subeuhedral or Subhedral, if only part is preserved. Anhedral or xenomorphic, if the crystals present no recognizable crystallographic forms.
In geology, a xenomorph or allotriomorph is a mineral that did not develop its otherwise typical external crystal form because of late crystallization between earlier formed crystals. Xenomorphs are typical of matrix minerals in rapidly crystallizing volcanic lavas and shallow igneous intrusions.
Microcline may be chemically the same as monoclinic orthoclase, but because it belongs to the triclinic crystal system, the prism angle is slightly less than right angles; hence the name "microcline" from the Greek "small slope". It is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase. Microcline is ...
Pyrrhotite typically appears as anhedral, granular aggregates and is cream-pink to brownish in color. [20] Weak to strong reflection pleochroism which may be seen along grain boundaries. [ 20 ] Pyrrhotite has similar polishing hardness to pentlandite (medium), is softer than pyrite, and harder than chalcopyrite. [ 20 ]
Blossite occurs as black anhedral crystals, with dimensions not exceeding 150 um. Crystals of blossite have only been isolated with other fumarolic copper vanadates or sulfates. Blossite demonstrates a red-brown streak, prevalent to the natural copper present, this red-brown coloring is also a prevalent in the internal reflections.