MINERAL: Limonite (mixture of hydrated lepidocrocite, goethite, and hematite)
COLLECTION_LOCALITY: Tuscaloosa County, Alabama
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
Original spectrum published in: 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.
With the note:"Much limonite is actually cryptocrystalline goethite or lepidocrocite along with along with hematite, and additional water in some form. Colloidal silica, organic material, phosphates and clay minerals are also often present. Consequently, the name limonite is usually used as a field term for poorly characterized hydrated ferric oxide material. The water content of limonite is variable, but it typically contains 12% to 14% water by weight (Deer and others, 1962). This particular sample displays the change from opaque to transparent behavior near 0.55µm, and the band near 0.9µm typical of the ferric oxides. Because this sample is more transparent, these features are much more clearly resolved here. It also shows quite clearly the water of hydration bands near 1.4 and 1.9 µm for the larger particle size samples."
Goethite - major
No evidence of hematite
Konnert, Judith and Marta Flohr, 1992, unpublished data, USGS Reston, VA.
Goethite (major), Quartz (trace) S. Sutley, April, 2005.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem
SPECTRAL_PURITY: 1b2b3b4u # HS41.3 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns