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DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS28.3B
MINERAL_TYPE: Phyllosilicate
MINERAL: Biotite (Mica group)
FORMULA: K(Mg,Fe+2)3(Al,Fe+3)Si3O10(OH,F)2
FORMULA_HTML: K(Mg,Fe+2)3(Al,Fe+3)Si3O10(OH,F)2
COLLECTION_LOCALITY: Ontario
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
SAMPLE_DESCRIPTION:
Forms series with Phlogopite.
Usually in irregular foliated masses. Composition is similar to phlogopite but with considerable substitution of Fe+2 for Mg. There is also substitution by Fe+3 and Al for Mg and by Al for Si. In addition a series exists between phlogopite and biotite. The trioctahedral biotite structure is the same as that of phlogopite.
"S-5. Biotite. Bancroft, Ontario (28). A potassium magnesium-iron-aluminum silicate, essentially K(Mg,Fe)3AlSi3O10(OH)2. Biotite is a widely distributed accessory mineral in igneous rocks and also occurs in some metamorphic rocks. Ferrous and ferric ions cause a very broad band in the 0.6 to 1.5µm region, and the drop-off in the blue. Hydroxyl bands are barely observable in the spectra. There are several possible reasons for the lack of observable OH overtones in this spectrum: The OH groups are commonly oriented (because the mica flakes lie on their cleavage faces) so that the observation angle may preclude their observation in the spectrum; the fundamental OH stretch is normally much broader in biotite than in other micas; and the OH concentration in this sample may be particularly low, because the OH in biotite may be readily replaced by F, Na, Fe+2 etc."
Sieve interval 74 - 250µm.
Hunt, G.R., J.W. Salisbury, 1970, Visible and near-infrared spectra of minerals and rocks: I. Silicate minerals. Modern Geology, v. 1, p. 283-300.
IMAGE_OF_SAMPLE:
END_SAMPLE_DESCRIPTION.
XRD_ANALYSIS:
N. Vergo: Biotite plus trace other (pre 1990). New analysis by Steve Sutley, September, 2003 shows this is a pure titanium biotite. Thus, the spectral purity is raised from b to a.
Clark, R.N., King, T.V.V., Klejwa, M., Swayze, G.A., and Vergo, N., 1990, High spectral resolution reflectance spectroscopy of minerals: Journal of Geophysical Research, v. 95, no. 8B, p 12,653-12,680.
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: EM(WDA) # XRF, EPMA, ICP(Trace), WChem
| COMPOSITION KEYWORD |
Oxide ASCII |
Amount | Weight Percent, % |
Oxide html |
|---|---|---|---|---|
| COMPOSITION: | SiO2 | 38.00 | wt% | SiO2 |
| COMPOSITION: | TiO2 | 1.96 | wt% | TiO2 |
| COMPOSITION: | Al2O3 | 11.42 | wt% | Al2O3 |
| COMPOSITION: | FeO | 17.44 | wt% | FeO |
| COMPOSITION: | MnO | .83 | wt% | MnO |
| COMPOSITION: | MgO | 13.85 | wt% | MgO |
| COMPOSITION: | CaO | .01 | wt% | CaO |
| COMPOSITION: | Na2O | .56 | wt% | Na2O |
| COMPOSITION: | K2O | 8.91 | wt% | K2O |
| COMPOSITION: | Cl | .06 | wt% | Cl |
| COMPOSITION: | F | 4.90 | wt% | F |
| COMPOSITION: | Total | 97.12 | wt% | |
| COMPOSITION: | O=Cl,F,S | 1.74 | wt% | #correction for Cl, F, S |
| COMPOSITION: | New Total | 95.38 | wt% |
COMPOSITION_TRACE: None
COMPOSITION_DISCUSSION:
Average of 6 samples. (Done by Gregg Swayze)
END_COMPOSITION_DISCUSSION.
MICROSCOPIC_EXAMINATION:
Basal cleavage, slight pleochroism, pale green color, no mottled extinction, 1st order gray interference color, rod like inclusions (1-2 vol% sillimanite, length slow, straight extinction), biaxial (-), 2v about 30 degrees. Apart from lack of mottled extinction and low order interference color, all is consistent with this sample being biotite. G. Swayze.
END_MICROSCOPIC_EXAMINATION.
SPECTROSCOPIC_DISCUSSION:
END_SPECTROSCOPIC_DISCUSSION.
SPECTRAL_PURITY: 1a2a3a4a # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns