A proposed mechanism for the growth of chalcedony

Research output: Contribution to journalArticle

103 Citations (Scopus)

Abstract

The structural disparities that distinguish chalcedony from macrocrystalline quartz suggest that different crystallization mechanisms are operative during the growth of these two forms of silica. Although the paragenesis of chalcedony has provoked marked disagreement among researchers, a review of previous studies supports the idea that chalcedony can precipitate from slightly saturated aqueous solutions at relatively low temperatures (<100° C). These conditions for deposition suggest a model for chalcedony crystallization that involves the assembly of short-chain linear polymers via bridging silica monomers. This assembly occurs through a spiral growth mechanism activated by a screw dislocation with b=n/2 [110], where n is an integer. The proposed model can account for a number of peculiarities that have been observed in chalcedony at the microstructural scale, such as: (1) the direction of fiber elongation along [110] rather than [001]; (2) the periodic twisting of chalcedony fibers about [110]; (3) the high density of Brazil twin composition planes; (4) the common intergrowth of moganite within chalcedony.

Original languageEnglish (US)
Pages (from-to)66-74
Number of pages9
JournalContributions to Mineralogy and Petrology
Volume115
Issue number1
DOIs
StatePublished - Mar 1 1993

Fingerprint

chalcedony
Crystallization
Silicon Dioxide
assembly
crystallization
silicon dioxide
Screw dislocations
Quartz
fibers
Fibers
screw dislocations
twisting
Brazil
elongation
integers
Precipitates
Elongation
precipitates
Polymers
quartz

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

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A proposed mechanism for the growth of chalcedony. / Heaney, Peter J.

In: Contributions to Mineralogy and Petrology, Vol. 115, No. 1, 01.03.1993, p. 66-74.

Research output: Contribution to journalArticle

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