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: Epidote HS328 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS328.3B

MINERAL_TYPE: Sorosilicate

MINERAL: Epidote (Epidote group)

FORMULA: Ca2(Al,Fe+3)3(SiO4)3(OH)

FORMULA_HTML: Ca₂(Al,Fe⁺³)₃(SiO₄)₃(OH)

COLLECTION_LOCALITY: Arizona

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 Clinozoisite.

"S-3 Epidote 328B--Arizona. Ca₂(Al,Fe)Al₂O• OH(Si₂O₇)(SiO₄): This metamorphic mineral is the iron-rich end member of the clinozoisite-epidote series. The features are those due to both ferrous and ferric iron at 0.41, 0.47, near 0.6 µ and 1.0 µ. Again, the hydroxyl features are unusual. The feature at 1.55 µ appears, and it is accompanied by a very weak feature at 1.4 µ (not discernible in reproduced spectrum). The two features near 1.85 µ and 1.9 µ, like those in zoisite, are apparent, as is a very intense feature at 2.35 µ with well defined side features."

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, v. 4, p. 85-106.

Grain size fractions are indicated by the extension after the sample number:
.3B = 74-250 µm

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Spectrally pure. Epidote plus a large amount of quartz plus a small amount other; M: ~2% magnetite on epidote, ~15% quartz, ~3% plagioclase, no carbonate. (Norma Vergo)

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

mode:
80 vol% epidote
15 vol% quartz
3 vol% plagioclase ?
2 vol% magnetite

average grain size= 250 µm

Epidote grains are highly fractured or polygranular, with quartz intergrowths on about 10% of epidote grains. Individual crystal grain size is about 50 µm or less because of polygranular and fractured nature. Determination of optical properties is difficult because of fractures and polygranular nature.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2b3c4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns