cryptocrystalline


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cryptocrystalline

[¦krip·tō′krist·əl·ən]
(geology)
Having a crystalline structure but of such a fine grain that individual components are not visible with a magnifying lens.

cryptocrystalline

A rock texture that is too fine to be discernible with an optical microscope.
References in periodicals archive ?
As noted earlier, blue/purple cryptocrystalline encrustations also believed to be vivianite have been found on the creek cut bank clays and on gravel of the point bar.
In thin section the altered lava flows looks like a cryptocrystalline mass where clay minerals normally appear as massive fine aggregates mixed with shards.
Galena is present mainly as the common coarse-grained, well-crystallized and friable type, but also displays several other textures, such as fine-grained, sheared, massive, and 'steel' (a dense, extremely fine-grained, almost cryptocrystalline type).
The first lithotype is represented by grey to brownish-grey, micro- to cryptocrystalline, medium- (2-10 cm) to thick-bedded (>10 cm), seminodular to nodular limestones.
Petrographic observation of the samples analyzed in the present study, as well as the samples studied by Plymate and others (1992) and Plymate and others (2001), reveals that the feldspars are significantly clouded by alteration to cryptocrystalline clays, mica, and/or hematite.
Both magnetic metallic crystalline and nonmagnetic cryptocrystalline glass MS were separated from sediments excavated from what appears to be the bottom of a late Pleistocene or early Holocene ice dam lake situated along the banks of the Colorado River about two and one-half miles west of the Colorado-Utah state line.
Chinese magnesite is not able to compete with super magnesite made from brine magnesite and natural cryptocrystalline magnesite in the world market.
The main types include sulphide reef (massive sulphide enclosing clasts of quartz and feldspar), siliceous reef (fine sulphide in a banded cryptocrystalline quartz matrix and sometimes associated with altered feldspar porphyroblasts), mylonitic reef (streaky sulphide in a biotite-chlorite host) and mineralized country rock (fine sulphide in granulite).
Gold mineralization occurs primarily in altered, pyrite-bearing argillites and occasionally siltstones, and in the underlying massive sandstones with zones of grey cryptocrystalline quartz veining and strong silicification.
The connection between the Baltoscandian and Moscow basins obviously broke off in the early Katian corresponding to the Nabala Stage, because the lithology of the sediments overlying the widespread cryptocrystalline limestones of the Rakvere Stage differs from that in the neighbouring Russian areas.
The ore microscope observation shows that the matrix mineral components in the bauxite ores are cryptocrystalline diaspore, hematite, ferrohydrite, kaolinite, anatase, vanadium titanomagnetite and chamosite (Figs.