CaltechAUTHORS
Published June 2007 | Version public
Journal Article Metadata-only

The origin of color in "fire" obsidian

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon GeoEngineers (United States)

Abstract

A variety of obsidian from Glass Buttes, Oregon, known as "fire" obsidian and named for thin layers showing various colors, was investigated with field-emission scanning electron microscopy, X-ray energy-dispersive spectroscopy, electron back-scatter diffraction, and optical spectroscopy methods. Our study reveals that the thin layers mainly consist of concentrated nanometric crystals of magnetite. The thin layers, which have a thickness of 300 to 700 nm, give rise to brilliant colors in reflection. The color is caused by thin-film optical interference, in which the thin layers have a higher calculated index of refraction (1.496 < n < 1.519) than that of the host glass (n = 1.481).

Additional Information

© 2007 Mineralogical Association of Canada. Received January 6, 2006; revised manuscript accepted September 15, 2006. FE–SEM, EDS and EBSD analyses were done at the Caltech GPS analytical facility, which is supported in part by the MRSEC Program of the NSF under DMR–0080065. Additional support was provided to G.R.R. through NSF grant EAR–0337816.

Additional details

Identifiers

Eprint ID
38103
DOI
10.2113/gscanmin.45.3.551
Resolver ID
CaltechAUTHORS:20130424-151411897

Related works

Describes
10.2113/gscanmin.45.3.551 (DOI)

Funding

NSF Materials Research Science and Engineering Center (MRSEC)
DMR-0080065
NSF
EAR-0337816

Dates

Created
2013-04-25
Created from EPrint's datestamp field
Updated
2021-11-09
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Division of Geological and Planetary Sciences (GPS)