TITLE: Annite WS660 Biotite DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS660

MINERAL_TYPE: Phyllosilicate

MINERAL: Annite (Mica group)

FORMULA: K(Fe+2)3AlSi3O10(OH,F)2

FORMULA_HTML: KFe+23AlSi3O10(OH,F)2

COLLECTION_LOCALITY: Bancroft, Ontario, Canada

ORIGINAL_DONOR: Wards Scientific

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

The sample appears uniform dark green and the visible-NIR spectrum shows strong iron bands and a spectrum typical of pure annite.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Triocathedral mica - major - probably a mixture of compositions. No other components.

Konnert, Judith and Marta Flohr, 1992, unpublished data, USGS Reston, VA.

40 kV - 30 mA, 7.3-9.5 keV
File: annit660.out, -.mdi (edge=random mount)
References: Huebner's reference patterns; JCPDS #42-1413, 33-1016
Found: trioctahedral mica, 3T or 1M polytype

Comment: Basal reflections are surprisingly weak, even considering the use of a random mount. Some peak broadening or splitting suggests compositional heterogeneity of zoning. The position of the (060) is consistent with Fe/(Mg+Fe+Mn) = 0.25 +/- 0.05 (phlogopite), but not annite or siderophyllite.

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

END_XRD_ANALYSIS.

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


COMPOSITION: SiO2 39.526 wt% SiO2
COMPOSITION: TiO2 2.042 wt% TiO2
COMPOSITION: Al2O3 11.052 wt% Al2O3
COMPOSITION: FeO 16.995 wt% FeO
COMPOSITION: MnO 0.693 wt% MnO
COMPOSITION: MgO 14.456 wt% MgO
COMPOSITION: CaO 0.008 wt% CaO
COMPOSITION: Na2O 0.607 wt% Na2O
COMPOSITION: K2O 9.668 wt% K2O
COMPOSITION: Cl 0.052 wt% Cl
COMPOSITION: F 3.181 wt% F
COMPOSITION: Total 98.281 wt%
COMPOSITION: O=Cl,F,S wt% #correction for Cl, F, S
COMPOSITION: New Total wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Bimodal grain size distribution:

population 1 av gr sz = 300µm 80 vol%
population 2 av gr sz = 10µm 20 vol%

av gr sz of populations = 270µm

Pure annite with larger grains 80% coated by smaller grains. Micaceous flakes with avg. flake diameter = 20µm. Biaxial (-), larger 2V, slight pleochroism, single good basal cleavage. G. Swayze

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 435 0.2-3.0µm 200 g.s.= 270 µm

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

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