Original paper
Structural characteristics of agates and their genetic significance.
Landmesser, Michael
Neues Jahrbuch für Mineralogie - Abhandlungen Band 159 Heft 3 (1988), p. 223 - 235
47 references
published: Sep 16, 1988
DOI: 10.1127/njma/159/1988/223
ArtNo. ESP154015903001, Price: 29.00 €
Abstract
Detailed petrographic studies of characteristic macroscopic and microscopic structures in agates are used to elucidate the mechanism and the physico-chemical conditions of agate genesis. It is shown that Uruguay-agates may not be used as geothermometers concerning the critical temperature of water or aqueous solutions. New structural features of agates are reported and their genetic significance is discussed. The most reasonable medium of agate genesis is a polydispersed colloidal silica system. The formation of different agate structures in such a system is described. General questions of pattern formation in natural inorganic systems are broached. An example of a self-patterning process in a natural inorganic system (nascent agate system) is given by the detection of rhythmic precipitations in some agates.
Keywords
Agate • silica • pattern formation • Liesegang rings • genesis • morphology • colloidal systems • geological thermometer • spherulites • self-organization