TITLE: Epidote GDS26 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS26

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: Prince of Wales Island, Alaska

ORIGINAL_DONOR: Bruce Hemingway

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Clinozoisite.

"Results of petrographic examination: Deep green colored epidote crystals 2 cm x 1 cm in size. Looks pure. Microscopic examination indicates pure clean epidote with no alteration."

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

Sample is in two sieve intervals: (a) 75-200µm and (b) <75µm.

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)

"Epidote plus a trace of quartz. No quartz bands are apparent in the spectrum; however, spectral features due to trace of a carbonate were seen and the sample was given acid treatment to remove this contaminent."

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EM(WDS) # XRF, EM(WDS), ICP(Trace), WChem


COMPOSITION: SiO2 37.14 wt% SiO2
COMPOSITION: TiO2 0.16 wt% TiO2
COMPOSITION: Al2O3 23.05 wt% Al2O3
COMPOSITION: FeO 14.5 wt% FeO
COMPOSITION: MnO 0.18 wt% MnO
COMPOSITION: MgO 0.06 wt% MgO
COMPOSITION: CaO 22.85 wt% CaO
COMPOSITION: Na2O 0.01 wt% Na2O
COMPOSITION: K2O 0.02 wt% K2O
COMPOSITION: Total 97.97 wt%
COMPOSITION: O=Cl,F,S wt% #correction for Cl, F, S
COMPOSITION: New Total wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Microprobe analysis indicates that the sample is homogeneous within and between grains, and has typical epidote composition.

Salisbury, J. W., Walter, L. W., and Vergo, N., 1987, Mid-Infrared (2.1-25µm) Spectra of Minerals: First Edition, U.S. Geological Survey Open File Report 87-263.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

75 < x < 200 µm fraction:
mode:
94 vol% epidote
5 vol% quartz
1 vol% plagioclase

avg gr sz = 171 µm

Green pleochroism, pistachio green color, perfect cleavage, biaxial (-), high relief, all consistent with epidote.

< 75 µm fraction:
mode:
50 vol% epidote
50 vol% quartz (uniaxial (+), low order grey)

Bimodal gr sz distribution:
pop 1 50 µm 40 vol%
pop 2 7 µm 60 vol%

avg gr sz for entire population = 32 µm

Note: < 75 µm fraction significantly contaminated with quartz. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1_2_3_4_

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment

LIB_SPECTRA: splib04a r 1552 0.2-3.0µm 200 g.s.= 171 µm
LIB_SPECTRA: splib04a r 1564 0.2-3.0µm 200 g.s.= 32 µm

LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=

LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=