Occurrence and distribution of “moganite” in agate/chalcedony: a combined micro-Raman, Rietveld, and cathodoluminescence study

Götze, Jens; Nasdala, Lutz; Kleeberg, R.; Wenzel, M.

doi:10.1007/s004100050440

Cited by 141 publications

(180 citation statements)

References 0 publications

Supporting

Mentioning

169

Contrasting

Unclassified

Order By: Relevance

“…The result gives moganite an advantage of crystallization from hydrous amorphous silica because moganite possesses the cis configuration in the structure. (Götze et al, 1998). The Raman band integral ratio in the present study is shown by a solid star.…”

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 57%

“…, using a method proposed by Götze et al (1998). The resultant Raman band integral ratio I (501 cm−1) /I (465 cm−1) is 20.3%, which suggests that the moganite content approaches about 50 wt% (Fig.…”

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 97%

“…This is responsible for the textural transformation from chalcedony to quartz. Götze et al (1998) presented evidence of single bands in agates that suggest alternating formation of fine-grained, highly defective chalcedony intergrown with moganite, and coarse-grained low-defect quartz. On the other hand, impurities may promote Brazil twinning since cations can occupy the sites of bridging tetrahedra (McLaren and Pitkethly, 1982).…”

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 99%

See 2 more Smart Citations

Pressure–induced crystallization of biogenic hydrous amorphous silica

Kyono

Yokooji

Chiba

et al. 2017

Journal of Mineralogical and Petrological Sciences

View full text Add to dashboard Cite

Samples of the diatom Nitzschia cf. frustulum, collected from Lake Yogo, Siga Prefecture, Japan, were cultured in the laboratory. Organic components of the diatom cell were removed by washing with acetone and sodium hypochlorite. The remaining frustules were studied by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier-transform infrared (FTIR) spectroscopy, and synchrotron X-ray diffraction. The results showed that the spindle-shaped diatom frustule was composed of hydrous amorphous silica. Pressure-induced phase transformation of the diatom frustule was investigated by in situ Raman spectroscopic analysis. With exposure to 0.3 GPa at 100°C, the Raman band corresponding to quartz occurred at ν = 465 cm −1 . In addition, a characteristic Raman band for moganite was observed at 501 cm −1 . From the integral ratio of Raman bands, the moganite content in the probed area was estimated to be approximately 50 wt%. With increased pressure and temperature, the initial morphology of diatom frustules was totally changed to a characteristic spherical particle with a diameter of about 2 µm. Increasing pressure to 5.7 GPa at 100°C resulted in the appearance of a Raman band assignable to coesite at 538 cm −1 . That is, with compression and heating, hydrous amorphous silica can be readily crystallized into quartz, moganite, and coesite. First-principles calculations revealed that a disiloxane molecule with a trans configuration is twisted 60°with a close approach of a water molecule, which leads to a trans to cis configuration change. It is therefore reasonable to assume that during crystallization of hydrous amorphous silica, an Si-O-Si bridging unit with the cis configuration would survive as a structural defect, and could subsequently crystallize into moganite by maintaining that geometry. This hypothesis is adaptable to the phase transformation from hydrous amorphous silica to coesite as well, because coesite has four-membered rings and is easily formed from hydrous amorphous silica under high pressure and temperature conditions.

show abstract

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 57%

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 97%

Section: Structural and Morphological Changes Of Biogenic Hydrous Amomentioning

confidence: 99%

See 1 more Smart Citation

Pressure–induced crystallization of biogenic hydrous amorphous silica

Kyono

Yokooji

Chiba

et al. 2017

Journal of Mineralogical and Petrological Sciences

View full text Add to dashboard Cite

show abstract

“…Kingma & Hemley, 1994;Götze et al, 1998, Burgio & Clark, 2001) revealed the presence of the mineral species summarised below:…”

Section: Resultsmentioning

confidence: 99%

“…However the proportion of moganite varied from very poor to very rich with I 502 /I 465 = ~ 35% in NAM 4928. The proportion of moganite is a key crystallographical/petrographical feature that may help to locate the geological provenances of these stones (Kingma & Hemley, 1994;Götze et al, 1998).…”

Section: Resultsmentioning

confidence: 99%

A Mineralogical Study of Some Mycenaean Seals Employing Mobile Raman Microscopy

Economou¹,

Konstantinidi-Syvridi

Kougemitrou³

et al. 2017

geosociety

View full text Add to dashboard Cite

show abstract

Applications of Vibrational Spectroscopy to Geology

Gillet

2001

Handbook of Vibrational Spectroscopy

View full text Add to dashboard Cite

The sections in this article are Introduction Vibrational Spectra of Minerals, Glasses and Fluids: Basic Aspects Minerals: The Example of Carbonates Glasses: The Example of Si O 2 Fluids Micro‐ R aman and Micro‐Infrared Spectroscopy Micro‐ R aman Spectroscopy Micro‐Infrared Spectroscopy Vibrational Spectroscopy of Minerals at High Pressure and Temperature The Diamond Anvil Cell Vibrational Spectroscopy at Elevated Temperatures Some Examples in the Si O 2 System From Vibrational Spectra of Minerals to Thermodynamic Properties Spectroscopic Data for Some Representative Mineral Groups Simple Minerals: Diamond, Graphite, Alkali Halides, Mg O , Ti O 2 and Simple Hydrous Phases Si O 2 Polymorphs and Glass Orthosilicates Feldspars, Feldspathic Glasses and Other Framework Aluminosilicates Chain Silicates: Pyroxenes and Amphiboles Sheet Silicates: Micas, Clays and Serpentines Pyrosilicates Ring Silicates Corundum and Ilmenite Perovskites Spinels Carbonates Phosphates Sulfates and Sulfides Conclusion Acknowledgments

show abstract

Occurrence and distribution of “moganite” in agate/chalcedony: a combined micro-Raman, Rietveld, and cathodoluminescence study

Cited by 141 publications

References 0 publications

Pressure–induced crystallization of biogenic hydrous amorphous silica

Pressure–induced crystallization of biogenic hydrous amorphous silica

A Mineralogical Study of Some Mycenaean Seals Employing Mobile Raman Microscopy

Applications of Vibrational Spectroscopy to Geology

Contact Info

Product

Resources

About