Clark et. al. 2003 USGS Open File Report 03-395
Spectral Library splib05a Sample Description

(For further information on spectrsocopy, see: http://speclab.cr.usgs.gov)

TITLE: Fassaite HS118 Pyroxene DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS118

MINERAL_TYPE: Inosilicate

MINERAL: Fassaite (Pyroxene group)

FORMULA: Ca(Mg,Fe+3,Al)(Si,Al)2O6

FORMULA_HTML: Ca(Mg,Fe⁺³,Al)(Si,Al)₂O₆

COLLECTION_LOCALITY: Helena, MT

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Primarily pyroxene; best matches are diopside and augite, but this is not definitive. Some amphibole and some chlorite present. Trace of an unidentifiable residual.

Konnert, Judith and Marta Flohr, 1992, unpublished data, USGS Reston, VA.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Fassaite commonly contains Fe⁺³ which results in an absorption feature at 0.85µm and ferrous iron which results in a weak band near 1.05µm.

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.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

mode:
90 vol% clinopyroxene (light green)
5 vol% clinopyroxene (dark green)
5 vol% magnetite
trace Fe-oxide staining

average grain size = 292 µm

Smaller grains about 8 µm in diameter coat larger grains up to 15% of their surfaces. Magnetite occurs as inclusions in pyroxene grains. Two cleavages at nearly 90 degrees, biaxial (+), 2V ~ 60 degrees, inclined extinction, pleochroism most intense in darker green grains and I believe all one pyroxene. All these properties are consistent with clinopyroxene, and the 2V is about right for Fassaite. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

LIB_SPECTRA_HED:	where	Wave Range	Av_Rs_Pwr	Comment
LIB_SPECTRA:	splib04a r 1637	0.2-3.0µm	200	g.s.= 292 µm
LIB_SPECTRA:	splib05a r 2676	0.2-3.0µm	200	g.s.=

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