colloform

colloform

[′käl·ə‚fȯrm]
(geology)
Pertaining to the rounded, globular texture of mineral formed by colloidal precipitation.
References in periodicals archive ?
Veins range from less than 1 m to over 30 m in thickness and consist of quartz, chalcedony, calcite and pyrite, often showing banded, colloform, crustiform, vuggy and/or brecciated textures.
At the Area 8 prospect, surface rock-chips have returned assay results to 0.65 g/t gold, 106 g/t silver, 397ppm arsenic and 837ppm antimony from crustiform and colloform quartz veins and quartz breccia in-fill.
Field evidence, ore microscopy, and electron microprobe analyses of the lodes suggest that the vein mineralization commenced with pre-ore precipitation of diagenetic marcasite, pyrite, and minor gel-like colloform textured schalenblende and galena particularly in the vein--wall contacts (Akande and Mucke, 1993).
The outer margins may show colloform bands of fine micritic zones with variation in color due to different grain size and iron content (Fig.
Trace and minor element variations and sulfur isotopes in crystalline and colloform ZnS: Incorporation mechanisms and implications for their genesis.
The marcasite forms thick colloform coatings of iridescent crystals on matrix pieces from thumbnail to large-cabinet size, and a fine miniature could be had for around $40.
The manganese mineralization occurs mainly as nodules within the sedimentary section, and both Mn and Fe minerals exhibit colloform textures.
Three ore types are recognized texturally; (i) fine grained disseminated, (ii) coarse grained colloform banded and (iii) complex fine and coarse replacive.
This mineral assemblage is found in hydrothermal breccia veins and exhibits colloform textures consistent with low-sulphidation epithermal systems.
with a colloform structure" (Frommurze et al., 1940).