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Having very minute crystals.
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Legend for Figs 3 and 6-8: 1, limestone (wackestone and packstone); 2, dolomitic argillaceous bioclastic limestone (wackestone and packstone); 3, argillaceous limestone (wackestone and packstone); 4, cryptocrystalline limestone (calcareous mudstone); 5, bioclastic limestone (packstone); 6, bioclastic limestone (grainstone); 7, calcareous marlstone; 8, calcareous marlstone with rare bioclastic material; 9, argillaceous marlstone; 10, dolomitized argillaceous marlstone; 11, pyritized discontinuity surface; 12, limestone nodule.
Red earthy gravels also exhibited a cryptocrystalline fabric, but with a much lower degree of impregnation by oxides, which were concentrated near pores or surfaces between light-coloured domains, forming a reticulate pattern (Fig.
The Magnesites produced during these processes usually are in isotropic and cryptocrystalline forms, often with high grade.
Its limestone section is mainly mudstone and wackstone and can be light gray, off white, light grayish brown, soft, amorphous, cryptocrystalline to microcrystalline, chalky in parts, moderately argillaceous and having no visible porosity.
You won't see any crystal structure in this green stone as it's a cryptocrystalline mineral with the slightly ungainly name of chrysoprase, cryptocrystalline referring to the microscopic nature of its crystals.
Blue to purple cryptocrystalline encrustations, also believed to be vivianite, have been found on the clay sediments of the river bank just upstream from the point bar and on gravel on the point bar.
Crystals are small (<3 mm maximum diameter) and include rounded embayed quartz, subhedral K-feldspar (anorthoclase, based on the presence of fine-scale cross-hatch twinning), and subhedral plagioclase set in a locally spherulitic groundmass of cryptocrystalline quartz and feldspar.
The rocks are hypocrystalline, with phenocrysts mainly of plagioclase and pyroxene in a glassy and cryptocrystalline matrix.
Cryptocrystalline silica (opal) can precipitate in close proximity to pyrite, and is thought to be derived from weathering of layer aluminosilicate minerals.
As silicified wood and jasper are present in small numbers and are similar cryptocrystalline rocks, they are combined for this analysis.
Jasper is an opaque, impure cryptocrystalline quartz, usually red, but also yellow, green, and greyish blue in color.
Differences in reaction products morphology are also observed: their structures range from isotropic to cryptocrystalline.