Sample Description USGS Spectral Library Version 7

USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
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TITLE: Datolite HS442 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS442.1B, HS442.2B, HS442.3B, HS442.4B

MINERAL_TYPE: Nesosilicate

MINERAL: Datolite

FORMULA: CaBSiO4(OH)

FORMULA_HTML: CaBSiO₄(OH)

COLLECTION_LOCALITY: Connecticut

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"N-15 Datolite 442B--Conn. CaB(SiO₄)(OH): Datolite is typical of a mineral of secondary origin found in cavities in basaltic lavas and similar rocks. Its spectrum is completely dominated by well-resolved features near 1.02 µ , 1.26 µ, 1.48 µ, 1.74 µ, and 1.80 µ as well as multiple bands between 2.1 and 2.5 µ. The overall appearance of this spectrum from 0.6 to 1.85 µ is essentially identical with that of gypsum (see Part IV, p. 7-8, spectra SS 11-A through D) including the unusual 1.7 µ feature, although all the features in datolite are shifted slightly to longer wavelengths from the corresponding positions in gypsum. However, in datolite the intense 1.9 µ feature, indicative of the presence of molecular water is completely absent, and yet the spectrum of gypsum is explained entirely in terms of its molecular water of crystallization, with the 1.7 µ feature involving librational modes of water. It would seem therefore, in the absence of water that the bands short of 1.85 µ in datolite must be due to combination modes of at least two different types of OH stretching vibrations. The bands between 2.1 and 2.5 µ can be explained in terms of combination of these OH stretching modes with lattice modes with additional contributions from carbonate vibrations (due to calcite, which is present as an impurity) and possibly from combinations involving the boron-oxygen stretching modes (see Part V, p. 130-131, spectra B-1 through B-4)."

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.

Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Pure datolite (Norma Vergo).

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mode:
98 - 99 vol% Datolite
1 - 2 vol% Calcite
trace opaques

Biaxial (-), lacks cleavage, conchoidal fracture. All consistent with datolite. Sample should be washed with HCl to remove carbonate. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # Datolite HS442.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # Datolite HS442.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2b3b4b # Datolite HS442.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # Datolite HS442.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns