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USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
For more information on the library, see: local link web link

TITLE: Allanite HS293 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS293.1B, HS293.2B, HS293.3B, HS293.4B, HS293.6

MINERAL_TYPE: Sorosilicate

MINERAL: Allanite (Orthite, Epidote Group)

FORMULA: (Ce,Ca,Y)2(Al,Fe+3)3(SiO4)3(OH)

FORMULA_HTML: (Ce,Ca,Y)2(Al,Fe3+)3(SiO4)3(OH)

COLLECTION_LOCALITY: Ontario

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"Allanite is an accessory mineral in many granites, granodiorites, monzonites, and syenites, and occurs in large amounts in some limestone skarns and pegmatite's. It is typically a very dark mineral, and this sample is no exception. The high ferric iron and rare earth metal content reduces the reflectivity throughout the visible and very near infrared. The high metal ion content also quenches the hydroxyl bands."

Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, vol. 4, pp 85-106.

Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm
.6 = cut slab

IMAGE_OF_SAMPLE:
Photo of sample
END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.0-9.5 keV
File: allan293_mdi, *.out; allan2.out, *_mdi (smear mounts on quartz plate)
References: JCPDS #25-169
Found: metamict allanite

Comment: Few very weak, broad peaks correspond to those of allanite. Small amount of residual allanite; most of the sample has been damaged beyond X-ray diffraction recognition by autoradiation. J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mineral mode:

92 vol% Allanite, dark brown translucent, conchoidally fractured surfaces, lacks any good cleavage
5 vol% Fe-stained, conchoidally fractured, possibly quartz or sphene??
3 vol% White plagioclase, with 90 degree cleavage angle

population 1 Allanite: avg. grain size = 300µm
population 2 qtz-plag: avg. grain size = 290µm

avg. grain size of populations = 299µm

Dark brown grains are pleochroic, biaxial (-), lack good cleavage, have anomalous blue interference colors, and have high relief. All these are characteristic of allanite. G. Swayze

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

There is a slight increase in scattering at visible wavelengths in spectra of samples HS293.4B and HS293.6.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # HS293.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS293.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2b3c4_ # HS293.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS293.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS293.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns