Relationship between nanostructure and optical absorption in fibrous pink opals from Mexico and Peru

Research areas:

• Surfaces planétaires (2011 - 2016)

Year:

2004

Authors:

• E Fritsch
• E Gaillou
• M Ostroumov
• Benjamin Rondeau
• B Devouard
• A Barreau

Journal:

EUROPEAN JOURNAL OF MINERALOGY

Volume:

16

Number:

5

Pages:

743-751

Month:

SEP-OCT

ISSN:

0935-1221

BibTex:

@article{WOS:000224571200004, author = "E Fritsch and E Gaillou and M Ostroumov and Benjamin Rondeau and B Devouard and A Barreau", abstract = "Translucent pink opals from Mexico (states of Mapimi and Michoacan) and Peru (Acari area, near Arequipa) are opal-CT, containing from 10 to 40\% palygorskite, as demonstrated by XRD, infrared absorption and specific gravity measurements. Their nanostructure is unusual, with bunches of fibres 20 to 30 nm in minimum diameter, related to the fibrous nature of palygorskite crystals, as demonstrated by electron microscopy A complex absorption centred at about 500 nm is the cause of the pink colour. It is proposed that the absorption is due to quinone fossil products associated with the phyllosilicate fibres. The Raman spectrum of monoclinic palygorskite is deduced from that of its mixture with opal. The opal-CT-palygorskite-quinone association is a geological marker of a specific environment, presumably of a fossil lake environment in a volcanic region.", doi = "10.1127/0935-1221/2004/0016-0743", extra = "PICL", issn = "0935-1221", journal = "EUROPEAN JOURNAL OF MINERALOGY", month = "SEP-OCT", number = "5", pages = "743-751", title = "{R}elationship between nanostructure and optical absorption in fibrous pink opals from {M}exico and {P}eru", volume = "16", year = "2004", }

Abstract:

Translucent pink opals from Mexico (states of Mapimi and Michoacan) and
Peru (Acari area, near Arequipa) are opal-CT, containing from 10 to 40\%
palygorskite, as demonstrated by XRD, infrared absorption and specific
gravity measurements. Their nanostructure is unusual, with bunches of
fibres 20 to 30 nm in minimum diameter, related to the fibrous nature of
palygorskite crystals, as demonstrated by electron microscopy A complex
absorption centred at about 500 nm is the cause of the pink colour. It
is proposed that the absorption is due to quinone fossil products
associated with the phyllosilicate fibres. The Raman spectrum of
monoclinic palygorskite is deduced from that of its mixture with opal.
The opal-CT-palygorskite-quinone association is a geological marker of a
specific environment, presumably of a fossil lake environment in a
volcanic region.