Anhedral

Present in euhedral to anhedral forms (E-A), colloform (Collo.), pelletal (Pell.), columnar (Col.), dendritic (Den.). 

Monazite occurs as anhedral to subhedral masses associated with phyllosilicate-rich domains in massive sulfides. Masses display simple concentric zoning, a primary core, and commonly show fracturing and healing involving later generations of monazite growth that are likely a product of metamorphism (Fig. 2a). 

Anhedral pyrrhotite, from <10-200 pm in diameter, occurs in the matrix and in veins in all but one of the analysed samples. Visually the pyrrhotite appears to be inclusion-free, but Rare Pb- and Zr+REE-rich inclusions were found during analysis and it was noted that pyrrhotite in contact with pyrite generally has lower Co contents than other grains (3 ppm vs 280ppm, respectively, in samples from one drill hole) and have not been used for Interpretation. 

The U-Th minerals are large (>mm) anhedral crystals of Th-rich uraninite or uranothorianite with lobate contours. High Y2O3 contents (0.56 0.1 wt%) are also distinctive of the U-Th mineralization. 

XENOTOPIC. The fabric of a crystalline sedimentary rock in which the majority of the constituent crystals are anhedral. Fabric found in evaporites. chemically deposited cement, and recrystallized limestone or dolomite. 

Northwest Africa Oil (NWA 011) has briefly been described by Afanasiev et al. (2000) and more extensively by Yamaguchi et al. (2002), the source of most information presented here. NWA Oil is composed of relatively coarse, anhedral pigeonite and augite, and fine-grained, mostly interstitial plagioclase with a recrystallized texture, interpreted to indicate that it is a recrystallized breccia. Minor phases are silica, chromite, ilmenite, calcium phosphate, ferroan olivine, troilite, and baddeleyite. Pyroxenes make up... 

Pyrite and marcasite are the major minerals forming the sulfide cement, as identified by XRD and optical microscopy. These sulfides occur as both well-formed cubes and anhedral masses. Arsenic-rich areas (up to 1% by weight as estimated by EDS) occur in the pyrite and marcasite crystals as well as in iron hydroxides, but no separate arsenopyrite phase has been identified. Colloidal size (10-20 nm) iron hydroxide phases were identified using TEM. TEM-EDS analysis showed qualitative differences in arsenic, nickel, and zinc in the iron hydroxides on a nanometer scale. 

Granular Aggregates of anhedral crystals in matrix Scheelite... 

Calcite occurs as cement zones 10-150 cm thick. Pore-filling calcite crystals are anhedral blocky spar crystals (0.1-0.5 mm). In general, the petrographic appearance of basin margin calcite crystals is no different from calcite cements occurring in the basin centre. Some samples exhibit moderate to strong luminescence, whereas others are uniformly non-luminescent. 

An interesting feature of some saddle dolomite is the presence of anhedral inclusions of calcite ranging in diameter from < 1 pm to a few tens of micrometres. Using electron microprobe techniques, Radke Mathis (1980) documented the... 

Color/Luster Colorless to grayish white, also yellow to brown or black due to iron or foreign inclusions. Its luster is vitreous and transparent. Crystal System/Habit Isometric. Usually occurs as anhedral to subhe-dral crystals in a matrix. 

The severe acid treatments separated the aggregates into single crystals in a size range of 0.5-10/un with an average mean diameter of 3/xm. Twenty per cent of the crystals are euhedral acicular and the remainder are equant and anhedral. 

Some rocks yield only fractured and/or anhedral crystals. This seems especially common in gabbros, where apatites are often seen to be space-filling rather than euhedral. Such grains are difficult to use both because they make the a-ejection correction very difficult and because it is not obvious how to determine the original grain size. As a result the diffusion characteristics, which scale with grain size, are not well known. 

Photograph 3-5 Large, round, slightly ragged belite blue subhedral to anhedral alite and matrix of aluminate (CjA, arrow) and ferrite. Superimposed nital over KOH produces increased clarity in matrix phase definition. (S A6615)... 

Photograph 7-82 Free lime in clinker thin section. Crystals exhibit prominent cubic cleavage characteristic of free lime. An abundance of free-lime nests (some showing original limestone particle outline), anhedral alite, and extremely nonuniform distribution of silicates suggests poorly mixed coarse feed. Dry-process kiln, coal fired. (S A6700)... 

Facial development on crystals—euhedral, subhedral, anhedral areas of preferential development in a single clinker. 

Definition of species varieties and description— for example, raggedy, round, vs. dendritic varieties of belite or euhedral, large periclase vs. anhedral, or dendritic periclase state relative abundance and preferred locations of each. 

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