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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: Dumortierite HS190 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS190

MINERAL_TYPE: Nesosilicate

MINERAL: Dumortierite

FORMULA: Al7(BO3)(SiO4)3O3

FORMULA_HTML: Al7(BO3)(SiO4)3O3

COLLECTION_LOCALITY: Pershing, County, NV

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"Strong absorption feature near 0.5µm is due to pi-pi transition in the boron-oxygen triangle. OH bands occur at 1.4, 2.2 and 2.6 µm."

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.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA,6.5 -9.5 keV
File: dumor190_mdi, *.out; dumr190b_mdi, *.out (smear mounts on quartz plates)
References: Huebner's reference patterns; Borg and Smith (1969); JCPDS #7-71
Found: Quartz, minor dumortierite, minor additional phase(s)

Comment: Sharp peaks suggest high degree of crystallinity and compositional heterogeneity. The dumortierite pattern agrees well with that of hand-picked accicular lavender material from south of Alpine, San Diego County, CA (from the SSHuebner collection). HS190.3B shows reflections that are present in the pattern of the Alpine reference material but do not appear in the list of peaks calculated by Borg and Smith. We have not identified the reflections at 9.2, 5.57, 5.01, 4.53, 3.93, 3.53, 3.50, 2.776, 2.002, and 1.488 angstroms

J.S.Huebner, J. Pickrell, T.Schaefer, written communication (1994 USGS)

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mode:

47 vol% Feldspar or quartz (white, poor cleavage, hard, no twins)
35 vol% Dumortierite
10 vol% quartz
8 vol% muscovite

Bimodal grain size distribution:

pop1 average gr sz = 349 µm 99 vol%
pop2 average gr sz = 10 µm 1 vol%

Average grain sizes for entire population = 347 µm.
Intergrowths prevent giving grain sizes for individual minerals.

This sample is significantly contaminated by other minerals; however, except for the muscovite, all other contaminants may not contribute spectral absorptions. Fine-scale intergrowth of quartz and dumortierite make positive identification of quartz or feldspar very difficult. Strong violet-pink pleochroism in 35% of the grains, straight extinction and length fast (consistent with these grains being dumortierite but cannot get interference figures because pink grains are too fibrous).

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 1483 0.2-3.0µm 200 g.s.= 347 µm
LIB_SPECTRA: splib05a r 2495 0.2-3.0µm 200 g.s.=


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