TITLE: Desert_Varnish GDS78A DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS78A

MINERAL_TYPE: Mineral mixture (Birnessite + hematite and clays)

MINERAL: Desert_Varnish

FORMULA: Na4Mn14O27*9H20 + alpha-Fe2O3 + clays

FORMULA_HTML: Na4Mn14O27•9H2 + alpha -Fe2O3

COLLECTION_LOCALITY: Stoddard Wells, CA

ORIGINAL_DONOR: George Rossman, California Inst. of Techology

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"Desert varnish invariably consists of birnessite in intimate mixture with hematite and large amounts of clay minerals. The clays are generally of the illite-montmorillonite type with minor kaolinite, but in several samples this concentration ratio is reversed."

This sample is a coating on desert pavement rhyolite and quartz cobbles.

Potter, R.M. and G.R. Rossman, 1979, Mineralogy of manganese dendrites and coatings. American Mineralogist, v.64, pp 1219-1226.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

END_XRD_ANALYSIS.

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


COMPOSITION: SiO2 34.35 wt% SiO2
COMPOSITION: TiO2 0.78 wt% TiO2
COMPOSITION: Al2O3 20.01 wt% Al2O3
COMPOSITION: FeO 10.96 wt% FeO
COMPOSITION: MnO 22.63 wt% MnO
COMPOSITION: MgO 2.43 wt% MgO
COMPOSITION: BaO 1.22 wt% BaO
COMPOSITION: CaO 1.28 wt% CaO
COMPOSITION: Na2O 0.23 wt% Na2O
COMPOSITION: K2O 1.89 wt% K2O
COMPOSITION: P2O5 1.10 wt% P2O5
COMPOSITION: Total 96.88 wt%
COMPOSITION: O=Cl,F,S wt% #correction for Cl, F, S
COMPOSITION: New Total wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

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 1365 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.=