Clark and others 2007 USGS Data Series 231
Spectral Library splib06a Sample Description

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

TITLE: Nacrite GDS88 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS88

MINERAL_TYPE: Phyllosilicate

MINERAL: Nacrite (Kaolinite-Serpentine group)

FORMULA: Al2Si2O5(OH)4

FORMULA_HTML: Al₂Si₂O₅(OH)₄

COLLECTION_LOCALITY: Nayarite, Mexico

ORIGINAL_DONOR: Jim Crowley, USGS Reston, VA

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Polymorphous with Kaolinite, Dickite, and Halloysite.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: nacrt.out, -.mdi
References: JCPDS #16-606
Found: Nacrite; probable minor dickite; unidentified weak reflection at 2.80 Angstroms
Sought but not found: Kaolinite

Comment: The pattern closely matches that of nacrite (a polymorph of kaolinite). The (002) reflection at 7.2 Angstroms did not expand following glycolation. Of four reflections that are not nacrite, three (4.27, 3.79, 3.50 Angstroms) are in the position of dickite (another polymorph of kaolinite)

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

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

This sample appears to be nearly pure nacrite according to the XRD. The spectrum of the sample, however, shows a splitting of the 1.41µm feature into a major band near 1.40µm and a side band at 1.41µm. This suggest that the sample is a mixture of nacrite and dickite.

Crowley, James and Norma Vergo, 1986, Disorder in kaolin minerals: Observations using near-infrared reflectance spectroscopy. International Mineralogical Association Fourteenth General Meeting, Abstracts with Program, July 1986, Stanford University, Stanford, CA p. 84.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

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 3396	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib05a r 4840	0.2-3.0µm	200	g.s.=
LIB_SPECTRA:	splib06a r 15578			g.s.=