TITLE: Siderophyllite NMNH104998 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: NMNH104998

MINERAL_TYPE: Phyllosilicate

MINERAL: Siderophyllite (Mica group)

FORMULA: K(Fe+2)2Al(Al2Si2)O10(F,OH)2

FORMULA_HTML: KFe+22Al(Al2Si2)O10(F,OH)2

COLLECTION_LOCALITY: Brooks Mtns. Seward Peninsula, AK

ORIGINAL_DONOR: National Musuem of Natural History (Jim Crowley USGS)

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA and 6.5-9.5 keV (sidphyl.out, smear mount); 45 kV - 35mA and 7.3-9.5 keV (siphyl2.out, random or bulk mount)
References: Pattern for siderophyllite 1M in MSA Rev. Min. 13, p. 581; Huebner's reference pattterns for micas
Found: trioctahedral 1M mica, subordinate chlorite and calcite (X-ray); immersion oil examination chlorite >= mica >>> carbonate
Sought: quartz [(101) reflection obscured; a very weak peak observed in the position of the quartz (100)]

Comments: At least three phases present. The mica pattern is consistent with siderophylllite. Sharp reflections suggest mica is well crystallized and compositionally homogenous. The mica has a relatively large (002) spacing at 17.8, suggesting the presence of a large cation such as K. The chlorite (001) reflection is anomalously weak relative to the other chlorite reflections observed. Observed eight weak calcite reflections but found only a trace of carbonate in immersion oil, suggesting that the carbonate may not be homogenously distributed.

J.S. Huebner and J. Pickrell,T. Schaefer, unpublished data, written communication, USGS, Reston, VA (1994)

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

Since siderophyllite is volumetrically dominant according to my optical examination, I think it spectral signature will dominate over the chlorite. This is also so for calcite. However, it spectrum looks strikingly similar to thuringite SMR-15 shortward of 2.0µm. The 2.3-µm region has small band that are slightly shifted from thuringite (chlorite). This similarity may be coincidental, however, they may not be spectrally distinguishable shortward of 2.0µm. G. Swayze.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mode:

70 vol% Siderophyllite
15 vol% Chlorite
10 vol% Calcite
5 vol% Quartz
tr Fe-staining

Siderophyllite is biaxial (-) with small 2V angle and has a dark green color in plain polarized light. Other gains with basal cleavage have a lighter 1st order gray interference color and also are biaxial (-) with a small 2V. Calcite and quartz are also present in minor amounts. 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 4456 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.=