TITLE: Ilmenite HS231 DESCRIPT
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
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.
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
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
Not done yet
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 ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=