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: Ilmenite HS231 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS231

MINERAL_TYPE: Oxide

MINERAL: Ilmenite

FORMULA: Fe+2TiO3

FORMULA_HTML: Fe⁺²TiO₃

COLLECTION_LOCALITY: Norway

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Geikielite.

"O-10. Ilmenite. Norway (231B). Ilmenite, FeTiO₃, is sometimes found in veins or large masses as a product of magmatic segregation, and as beds or lenses in metamorphic rocks. Most commonly, it is an accessory mineral in igneous rocks, and it is frequently associated with the heavy fraction of beach and river sands. As in the case of this
sample, ilmenite is typically an opaque, almost spectrally featureless mineral in the visible and near-infrared. The relative reflectivity of the various particle sizes is typical of an opaque mineral--i.e., the smaller the particle size, the lower the reflectivity. Pure ilmenite is considered to be a titanate of ferrous iron (Fe²⁺ Ti⁴⁺O₃) rather than a double sesquioxide of ferric iron and titanium (Fe³⁺ Ti³⁺ O₃). In ilmenite ferric oxide is often present and can introduce features typical of the Fe³⁺ ion. When as little as 1% Ti is substituted in Fe₂O₃, the titanium acts as a donor and is all ionized to Ti⁴⁺ and Fe²⁺, and the Fe²⁺ produces a broad feature centered near 1.5µ. We have already observed a broad feature centered near 1.8µ in the pyroxenes (see Part I) which was attributed to the Fe²⁺ ion in a disordered octahedral site. The hydrated titanium ion (Ti³⁺ 6H₂O) produces a very broad spectral feature extending from 0.5µ into the infrared with a maximum at 2.0µ. The overall opacity of ilmenite is probably caused by a combination of all these features, broadened by defects, edge effects and the presence of impurities, as well as conduction bands due to both the iron and titanium extending out from the ultraviolet into the visible."

Sieve interval 74 - 250µm.

Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1971, Visible and near-infrared spectra of minerals and rocks: III. Oxides and hydroxides. Modern Geology, v. 2, p. 195-205.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
Files: ilmnt231.out, -.mdi, ground once; ilm231-2_*, ground twice; ilm231-3.*, same material as ilmnt231
References: JCDPS 29-733 (ilmenite) and 24-0074 (hematite); Huebner's reference patterns; SEM X-ray spectroscopy; light optical microscopy
Found: ilmenite, minor hematite and orthopyroxene, trace muscovite. Also weak unidentified reflections at 4.06, 2.94, 2.101, 2.028, 1.70, 1.44, and 1.395 Angstroms
Sought but not found: Quartz

Comment: Very well crystallized ilmenite and hematite. Observed hematite as exsolution lamellae in ilmenite using BSE imaging. Minor phases can fractionate from dense oxides during sample preparation, so their peak intensities are variable.

J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Not done yet

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2b3c4_ # 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 2403	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib05a r 3602	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib06a r 11099			g.s.=
LIB_SPECTRA:	splib06a r 11112			g.s.=