Clark and others 2007 USGS Data Series 231
Spectral Library splib06a Sample Description

(For further information on spectroscopy, see: http://speclab.cr.usgs.gov)

TITLE: Maghemite GDS81 Syn (M-3) DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS81

MINERAL_TYPE: Oxide

MINERAL: Maghemite (Synthetic, Hematite group)

FORMULA: gamma-Fe2O3

FORMULA_HTML: gamma-Fe₂O₃

COLLECTION_LOCALITY: Synthetic

ORIGINAL_DONOR: Not available

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

This sample is one of a series of sample synthesized for the following paper:

Sherman, D.M., R.G. Burns, and V.M. Burns, 1982, Spectral characteristics of the iron oxides with application to the Martian bright region mineralogy. Journal of Geophysical Research, v. 87, n. B12, pp. 10169- 10180.

Maghemite is formed either by the oxidation of magnetite or by the thermal dehydration of lepidocrosite.

The spectrum of our sample, M-3 most closely matches the spectrum of sample M-4A in the above paper. M-4 was produced by thermal oxidation of magnetite. The Mossbauer spectrum of that sample showed no evidence of a magnetite component. The X-ray patterns confirmed the identity of the sample and the TEM data indicated that the sample was well crystallized.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: maghmt81.out, -.mdi
References: Maghemite C (JCPDS 39-1346), Maghemite Q (JCPDS 12-1402) and Magnetite (Huebner's reference patterns).
Found: maghemite C, maghemite Q and/or magnetite; quartz

Comment: 5 very broad, very weak reflections correspond to a very poorly crystallized oxide phase, but the X-ray powder pattern does not reveal which one. The brown color suggest that magnetite, if present, is minor. Five reflections of quartz; the (100) and (101) are very sharp, suggesting well-crystallized quartz, rather than a precursor. What is quartz doing in a synthetic iron oxide preparation?? Could quartz have been added as a peak reference for XRD analysis by D. Sherman

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2b3b4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

LIB_SPECTRA_HED:	where	Wave Range	Av_Rs_Pwr	Comment
LIB_SPECTRA:	splib04a r 2842	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib05a r 4232	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib06a r 13124			g.s.=
LIB_SPECTRA:	splib06a r 13135			g.s.=