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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: Hornblende HS16 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS16

MINERAL_TYPE: Inosilicate

MINERAL: Hornblende (Amphibole group)

FORMULA: Ca2(Mg,Fe+2)4Al(Si7Al)O22(OH,F)2

FORMULA_HTML: Ca2(Mg,Fe+2)4Al(Si7Al)O22(OH,F)2

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:

Forms series from Magnesiohornblende to Ferrohornblende.

"I-22 Hornblende 16B--Ontario. (Ca, Na9K)2-3- (Mg, Fe2+, Fe3+, Al)5(Si6(Si, Al)2O22)(OH, F)2: Hornblende is the name given to a very complex series which varies with respect to at least ten major components. This spectrum is quite typical of hornblende spectra, which display a rapid fall off in intensity from 2.0µ to the blue due to broad Fe2+ and Fe3+ absorption near 0.7µ and 1.0µ. The hydroxyl band at 1.4 is also reduced in intensity or missing, leaving only OH features at 2.33µ and 2.4µ."

Sieve interval 74 - 250µm.

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_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: hnbld16.out, -.mdi
References: Borg and Smith (1969); Huebner's reference patterns
Found: clinamphibole, K-mica, trace chlorite (?), unindexed reflections at 3.02, 2.09, and 2.06 angstroms

Comment: The clinamphibole patterns is consistent with that of hornblende.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mode:
75 vol% Hornblende
20 vol% Chlorite (basal cleavage, 1st order gray, biaxial +)
5 vol% Plagioclase
trace Garnet

average grain size= 190 µm

Sample is significantly contaminated with other phases. Franz separator should work on this sample. Roger bets flat micas are pieces of hornblende, I say they are chlorite -- we bet a beer on this one. Hornblende has amphibole cleavage, strong green-blue pleochroism, OAP ll (010) ~ 30 degrees. All these properties are consistent with this being hornblende. Smaller > 10µm grains coat 10% of larger grain surfaces. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_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 2196 0.2-3.0µm 200 g.s.= 190 µm
LIB_SPECTRA: splib05a r 3332 0.2-3.0µm 200 g.s.=


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