TITLE: Talc HS21 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS21

MINERAL_TYPE: Phyllosilicate

MINERAL: Talc

FORMULA: Mg3Si4O10(OH)2

FORMULA_HTML: Mg3Si4O10(OH)2

COLLECTION_LOCALITY: Swain County, North Carolina

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"S-20. Talc. Swain Co., N.C. (21B). Talc is a hydrous magnesium silicate, essentially Mg3Si4O10(OH)2, of secondary origin. It may be found in altered igneous rocks, but is more typical of metamorphic varieties. It is formed by alteration of magnesian silicates such as olivine, pyroxenes and amphiboles. Talc may bear a little iron, aluminum or nickel, and ferrous ion in this talc probably accounts for the iron bands on either side of 1µ. The sample appears uncontaminated by unaltered pyroxene, which might otherwise contribute these bands. Hydroxyl bands are particularly strong and sharp in this sample, which displays them near 1.4µ and 2 to 2.6 µ. The extremely sharp, but weak feature at 0.95µ must also be due to OH."

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:

Talc + med. amount chlorite; M: ~2% chlorite, <<2% magnetite (Norma Vergo)

END_XRD_ANALYSIS.

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

COMPOSITION: SiO2 60.47 wt% SiO2
COMPOSITION: TiO2 0.04 wt% TiO2
COMPOSITION: Al2O3 0.12 wt% Al2O3
COMPOSITION: Fe2O3 0.87 wt% Fe2O3
COMPOSITION: FeO 0.10 wt% FeO
COMPOSITION: MnO 0.01 wt% MnO
COMPOSITION: MgO 30.29 wt% MgO
COMPOSITION: ZnO 0.00 wt% ZnO
COMPOSITION: BaO 0.01 wt% BaO
COMPOSITION: CaO 0.05 wt% CaO
COMPOSITION: Na2O 0.04 wt% Na2O
COMPOSITION: K2O 0.00 wt% K2O
COMPOSITION: P2O5 0.27 wt% P2O5
COMPOSITION: Cl 0.01 wt% Cl
COMPOSITION: F 0.51 wt% F
COMPOSITION: LOI 5.31 wt% LOI
COMPOSITION: Total 92.31 wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Because of variability in the analyses, most Fe is probably Fe+2.
Average of 6 point analysis.

NOTE: Conversion of Fe2O3 to FeO. This sample has too much chlorite. Therefore, Fe ratios are unusable.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

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 4687 0.2-3.0µm 200 g.s.=

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

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