Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-02T18:52:04.718Z Has data issue: false hasContentIssue false
  • English
  • Français

Agate and chalcedony from igneous and sedimentary hosts aged from 13 to 3480 Ma: a cathodoluminescence study

Published online by Cambridge University Press:  05 July 2018

T. Moxon  and
S. J. B. Reed
T. Moxon*
Affiliation:
55 Common Lane, Auckley, Doncaster DN9 3HX, UK
S. J. B. Reed
Affiliation:
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Chalcedony and agates from a variety of world-wide hosts have been examined using cathodoluminescence (CL). Gaussian fitting of the experimental data shows that there are two dominant spectral emissions at ∼400 and ∼660 nm. A third subordinate peak is also found at ∼470, ∼560 or ∼620 nm. An age-related link is shown between the respective decreasing and increasing relative intensities of the 660 and 620 nm emissions. It is proposed that this change is due to a condensation reaction between neighbouring Si–OH groups eliminating water and forming a strained Si-O-Si bond.

Agates from a variety of hosts and regions produced no clear demonstrable CL distinctions. However, a set of Western Australian agates was examined from host rocks that had been subjected to burial metamorphism. Cathodoluminescence produced different spectral emissions in the petrographic fibrous and granular regions of these agates. One agate shows a partial transformation of the petrographic fibrosity into granularity. This conversion is characterized by emission bands at 570 nm and 460 nm. Similar emission-band changes were produced by heating Brazilian agates for 35 days at 300°C. The identification of these changes in agate could serve as an indicator of palaeoheating within the parent rock.

Keywords

agatechalcedonycathodoluminescenceagesilanolwater
Type
Research Article
Information
Mineralogical Magazine , Volume 70 , Issue 5 , October 2006 , pp. 485 - 498
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2006

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Clark, R. (2002) Fairburn Agate Gem of South Dakota. Silverwind Agates, Appleton, USA, 104 pp.Google Scholar
Flörke, O. W., Köhler-Herbertz, B., Langer, K. and Tönges, I. (1982) Water in microcrystalline quartz of volcanic origin: Agates. Contributions to Mineralogy and Petrology, 80, 324–333.CrossRefGoogle Scholar
Gíslason, S. R., Heaney, P. J., Oelkers, E. H. and Schott, J. (1997) Kinetic and thermodynamic properties of moganite, a novel silica polymorph. Geochimica et Cosmochimica Acta, 61, 1193–1204.CrossRefGoogle Scholar
Götze, J., Nasdala, L., Kleeberg, R. and Wenzel, M. (1998) Occurrence and distribution of ‘moganite’ in agate/chalcedony: a combined micro-Raman, Rietveld, and cathodoluminescence study. Contributions to Mineralogy and Petrology, 133, 96–105.CrossRefGoogle Scholar
Götze, J., Plötze, M., Fuchs, H. and Habermann, D. (1999) Defect structure and luminescence behaviour agate-results of electron paramagnetic resonance (EPR) and cathodoluminescence (CL) studies. Mineralogical Magazine, 63, 149–163.CrossRefGoogle Scholar
Götze, J., Plötze, M. and Habermann, D. (2001) Origin, spectral characteristics and practical applications of the cathodoluminescence (CL) of quartz – a review. Mineralogy and Petrology, 71, 225–250.Google Scholar
Graetsch, H., Flörke, O. W. and Miehe, G. (1985) The nature of water in chalcedony and opal-C from Brazilian agate geodes. Physics and Chemistry of Minerals, 12, 300–306.CrossRefGoogle Scholar
Gries, J. P. and Martin, J. E. (1985) Composite outcrop section of the Paleozoic and Mesozoic strata in the Black Hills and surrounding areas. Pp. 261–292 in: Geology of the Black Hills, South Dakota and Wyoming (Rich, F. J., editor), American Geological Institute, Alexandria, Virginia, USA.Google Scholar
Heaney, P. J. (1993) A proposed mechanism for the growth of chalcedony. Contributions to Mineralogy and Petrology, 115, 66–74.CrossRefGoogle Scholar
Heaney, P. J. and Post, J. E. (1992) The widespread distribution of a novel silica polymorph in micro-crystalline quartz varieties. Science, 255, 441–443.CrossRefGoogle Scholar
House, M. (1989) Geology of the Dorset Coast. The Geologists’ Association, London, 170 pp.Google Scholar
Keller, P. C., Bockoven, N. T. and McDowell, F. W. (1982) Tertiary volcanic history of the Sierra del Gallego area, Chihuahua, Mexico. Geological Society of America Bulletin, 93, 303–314.2.0.CO;2>CrossRefGoogle Scholar
Lynne, B. Y., Campbell, K. A., Moore, J. N. and Browne, P. R. L. (2005) Diagenesis of 1900-year-old siliceous sinter (opal-A to quartz) at Opal Mound Roosevelt Hot Springs, Utah, U.S.A. Sedimentary Geology, 179, 249–278.CrossRefGoogle Scholar
Miehe, G. and Graetsch, H. (1992) Crystal structure of moganite: a new structure type for silica. European Journal of Mineralogy, 4, 693–706.CrossRefGoogle Scholar
Moxon, T. (2002) Agate: a study of ageing. European Journal of Mineralogy, 14, 1109–1118.CrossRefGoogle Scholar
Moxon, T. and Ríos, S. (2004) Moganite and water content as a function of age in agate: an XRD and thermogravimetric study. European Journal of Mineralogy, 16, 269–278.CrossRefGoogle Scholar
Moxon, T., Nelson, D. R. and Zhang, M. (2006) Agate recrystallization: evidence from samples found in Archaean and Proterozoic host rocks, Western Australia. Australian Journal of Earth Sciences, 53, 235–248.CrossRefGoogle Scholar
Nelson, D. R., Trendall, J. R., de Laeter, J. R., Grobler, N. J. and Fletcher, I. R. (1992) A comparative study of the geochemical and isotopic systematics of late Archaean flood basalts from the Pilbara and Knaapvaal cratons. Precambrian Research, 54, 231–256.CrossRefGoogle Scholar
Petrovic, I., Heaney, P. J. and Navrotsky, A. (1996) Thermochemistry of the new silica polymorph moganite. Physics and Chemistry of Minerals 23, 119–126.CrossRefGoogle Scholar
Stevens Kalceff, M. A. (1998) Cathodoluminescence microcharacterization of the defect structure of irradiated hydrated and anhydrous fused silicon dioxide. Physical Review B, 57, 5674–5683.CrossRefGoogle Scholar
Stevens Kalceff, M. A. and Philips, M. R. (1995) Cathodoluminescence microcharacterization of the defect structure of quartz. Physical Review B, 52, 3122–3134.CrossRefGoogle Scholar
Yamagishi, H., Nakashima, S. and Ito, Y. (1997) High temperature infrared spectra of hydrous microcrystalline quartz. Physics and Chemistry of Minerals, 24, 66–74.CrossRefGoogle Scholar