(For further information on spectrsocopy, see:
TITLE: Riebeckite HS326 Amphibole DESCRIPT
MINERAL: Riebeckite (Amphibole group)
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
"I-17 Riebeckite 326B--Colorado. Na2Fe32+Fe23+- (Si8O22)(OH, F)2: Riebeckite occurs in primary igneous rocks of acidic and intermediate composition. Ferric and ferrous iron produce the bands near 0.7µ and 0.975µ, and OH features appear at 1.4 and 2.35µ (again, there is a carbonate contribution to the latter band from slight calcite contamination). The small feature near 2.2µ is a hydroxyl-lattice combination band."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106.
40 kV - 30 mA, 7.0-9.5 keV
File: riebk326.mdi (smear on quarts plate)
References: PDF #23-1405, 45-1371, 33-1161, 21-1227; Borg and Smith (1969); Hawthorne (1981)
Found: Monoclinic amphibole, quartz, minor plagioclase, traces of chlorite and mica
Comments: Sharp peaks and good resolution of the alpha1-alpha2 components of the amphibole and quartz reflections suggest that these phases are well crystallized and that the amphibole is homogenous. Line-based search-match returns ferroan magnesiohornblende (45-1371), quartz, other amphiboles, and plagioclase feldspars. Profile based match-search returns quartz and the same magnesiohornblende as likely hits. Manual overlays of magnesiohornblende (45-1371), quartz (22-1161), albite (10-0393) or anorthite (41-1481), mica such as 1M-phlogopite (10-0495), and chlorite such as chamosite (13-0029) account for all but one observed reflections, at 3.058 angstroms. Cell refinement, using the quartz peaks as an internal standard, result in a=9.852(4), b=18.123(10), c=5.292(4) angstroms and beta=104.86(6) degrees. These dimensions suggest that the M4 site is occupied by Ca or Ca+Na (Hawthorns, 1981, fig. 43). Retrieval from the PDF2 database using the cell dimensions returns actinolite (41-1366), ferrotschermakite (43-0665), kaersutite (44-1450), magnesiohornblende (45-1371), tremolite (44-1402), and winchite (20-1390). The cell dimensions of HS-326 were compared with those of many amphiboles in the PDF2 database. This comparison eliminated riebeckite, magnesioriebeckite, glaucophane, and eckermannite, or their solid solutions as possibilities. The amphibole in HS-236 can be a solid solution of the many remaining amphibole components. The plagioclase, chlorite, and mica components of the pattern are too weak for the determination of composition or structure type.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
SPECTRAL_PURITY: 1d2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
|LIB_SPECTRA:||splib04a r 4252||0.2-3.0µm||200||g.s.=|
|LIB_SPECTRA:||splib05a r 5965||0.2-3.0µm||200||g.s.=|
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