subhedral


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subhedral

[¦səb¦hē·drəl]
(mineralogy)
Pertaining to an individual mineral crystal that is partly bounded by its own crystal faces and partly bounded by surfaces formed against preexisting crystals.
Descriptive of a crystal having partially developed crystal faces.
References in periodicals archive ?
Individual crystals form subhedral (predominant) to euhedral cubes and octahedra (which may be tightly intergrown in some areas) that do not exceed 0.
Samples from the host rocks contain 30 to 60 % anhedral quartz and subhedral and anhedral feldspar phenocrysts ranging from 5 to 12 mm in length (Fig.
Magnetite occurs in the sill rock as small black grains, and very rarely as black, crude subhedral crystals up to 5 mm in diameter.
The porphyritic monzogranite contains two populations of subhedral to euhedral feldspar phenocrysts (1-12 mm) with plagioclase generally more abundant than K-feldspar, constituting 30 35% of the rock.
Pyroxene: The pyroxene is mainly represented by both, ortho- and clinohypersthene, occurring as small euhedral to subhedral prismatic crystals and square or equant basal sections.
Fluorapatite has been found as a single, subhedral, yellow glassy crystal approaching 1 cm in a talcose matrix by Jon Ertmann in June 2002; identification was made by Bart Cannon using EDS.
No euhedral or subhedral rose quartz crystals have been described.
Instead, the subhedral shape of the calcite crystals suggests that they are pseudomorphs after gypsum and that the crystal-laminated interval exhibits a primary fabric that records little post-depositional deformation other than compaction.
The freshly exposed surfaces often contain as many as six different mercury minerals, ranging in habit from individual crystals to subhedral and anhedral masses, and also intimate mixtures displaying various colors.
Zircon grains recovered from the sample were mostly colourless to very pale brown and subhedral to anhedral in shape, the latter suggesting relatively late magmatic growth.
8 cm rises from a matrix of white subhedral microline crystals, sharp muscovite books and very dark smoky quartz crystals, the latter to 8 cm.