Sample Description USGS Spectral Library Version 7

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
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TITLE: Bronzite HS9 Pyroxene DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS9.1B, HS9.2B, HS9.3B, HS9.4B

MINERAL_TYPE: Inosilicate

MINERAL: Bronzite (ferroan Enstatite) (Pyroxene group)

FORMULA: (Mg,Fe+2)2Si2O6

FORMULA_HTML: (Mg,Fe⁺²)₂Si₂O₆

COLLECTION_LOCALITY: Jackson Co., North Carolina

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Spectrum displays double ferrous iron band typical of iron-rich orthopyroxenes.

Original spectrum published in:

Hunt, G.R., J.W. Salisbury, 1970, Visible and near-infrared spectra of minerals and rocks: I. Silicate minerals. Modern Geology, v. 1, p. 283-300.

"S-17E. Pyroxene, variety Bronzite. Jackson CO, N. Carolina (9B). This sample also displays the double ferrous ion band in the near-infrared typical of iron-rich orthopyroxenes. The slight band in the visible at 0.5µm is also a ferrous ion band."

Sieve interval 74 - 250µm.

Weak absorptions at 1.4 and 2.3 µm indicate trace alteration/contamination (probably tremolite). Roger N. Clark

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

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: brnzt9.out, -.mdi; brnzt9b.out, -.mdi (at low angles) (Both patterns obtained from smear mounts on quartz plates)
References: Huebner's reference patterns
Found: orthopyroxene, minor talc, trace chlorite (?), many un indexed moderately to very weak reflections (6.35, 5.25, 3.90, 3.58, 3.27, 3.23, 2.775, 2.255, 1.888, 1.643, and 1.580 Angstroms)

Comment: Sharp, strong pattern of orthopyroxene. Talc based on four basal reflections. Needs more work. END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

85 vol% Bronzite
10 vol% quartz (uniaxial +)
5 vol% green grains (augite?) and Fe-stained pyroxene

avg. grain size = 260 µm

Prismatic grains, two cleavages at near 90 degree angle, straight extinction, length slow, high relief, all consistent with orthopyroxene. Opaque inclusions in bronzite (< 1vol%). G. Swayze

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # Bronzite HS9.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # Bronzite HS9.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2c3c4c # Bronzite HS9.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # Bronzite HS9.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns