DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS86

MINERAL_TYPE: Phyllosilicate

MINERAL: Ammonium_Smectite (Synthetic)

FORMULA: (NH4)0.33(Al,Mg)2Si4O10(OH)2*nH2O

FORMULA_HTML: (NH₄)_0.33(Al,Mg)₂Si₄O₁₀(OH)₂•nH₂O

COLLECTION_LOCALITY: Synthetic

ORIGINAL_DONOR: Dennis Krohn, USGS Reston

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, 6.5-9.5 keV
File: amsmec86.mdi (smear on quartz plate)
References: PDF2 #13-0259 43-0688 33-1161; Brindley and Brown (1980)
Found: Possible dioctahedral ammonium smectite, quartz

Comment: All reflections are broad; the alpha1-alpha2 reflections of quartz are not resolved, even at high values of 2 theta. Clay reflections show only minor asymmetry toward smaller d-spacings. Search-match based upon strongest lines returned quartz and sepiolite, profile-based search-match returned quartz and rectorite. Neither pair satisfactorily explained the observed pattern. Manual search was initiated to identify the non-quartz peaks at 12.2, 4.46, ~3.23, ~2.57, and 1.499 angstroms by visual comparison with patterns of clay-type minerals. No single phase gave a good match. The most adequate fits were given by 14 angstroms montmorillonite (13-0259), which does not have a prominent reflection near 1.50 angstroms, and another dioctahedral smectite, volkonskoite, which does not account for the observed 3.27 angstrom reflection. The observed basal spacing, 12.2 angstoms, is smaller than the basal reflections of any other smectites in the PDF2 database. A summary table in Brindley and Brown (1980, p.203-204) shows that substitution of NH4 for any other interlayer cation reduces the basal spacings of a variety of smectites to 11.7-12.5 angstroms at 32-79 percent relative humidity, and slightly greater in water.

END_XRD_ANALYSIS.

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

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 311 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.=