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JPL Spectral Library

The JPL spectral library was originally published in Laboratory Reflectance Spectra of 160 Minerals, 0.4 to 2.5 Micrometers, by C.I. Grove, S.J. Hook, and E.D. Paylor II. The following description of the library and the preparation and measurement of the samples it contains is taken from that report. The report refers to the measurements made with the Beckman spectrometer. The same sample preparation and measurement procedure was used with the Nicolet spectrometer.

Table of Contents

1.0 INTRODUCTION

2.0 METHODOLOGY

    2.1 Sample Origin
    2.2 Sample Preparation
    2.3 X-ray Diffraction
    2.4 Electron Microprobe
    2.5 Spectrophotometer

3.0 REFERENCE

1.0 INTRODUCTION

This JPL Spectral Library includes laboratory reflectance spectra of 160 minerals in digital form. No attempt has been made to investigate the causes of the spectral features observed. Excellent theoretical studies dealing with the causes of these features are available in the open literature. One of the most comprehensive studies was published by Hunt and his coworkers in a series of papers between 1970 and 1979. Since then, several catalogues of reflectance spectra have been published, including Clark et al., 1990; Lang et al., 1990; and Urai et al., 1989.

Data for 135 of the minerals are presented at three different grain sizes: 125-500µm, 45-125µm, and <45µm. This study was undertaken to illustrate the effect of particle size on the shape of the mineral spectra. Ancillary information is provided with each mineral spectrum, including the mineral name, mineralogy, supplier, sampling locality, and our designated sample number. Generalized chemical formulae were obtained from Fleischer (1983) or electron microprobe analysis, when available. The purity of each mineral sample was evaluated by X-ray diffraction (XRD), and identifiable accessory minerals, if present, are noted with the ancillary information.

In the original publication the spectra were separated into classes according to the dominant anion or anionic group present, which is the classification scheme traditionally used in mineralogy. This format has been followed with the organization of the ftp site and each mineral class is a separate subdirectory. Classes include arsenates, borates, carbonates, elements, halides, hydroxides, oxides, phosphates, silicates, sulphates, sulphides and tungstates. The silicate class has been subdivided further into subclasses based on the degree of polymerization of the silicon tetrahedra. These subclasses include cyclosilicates, inosilicates, nesosilicates, phyllosilicates, sorosilicates and tectosilicates.

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2.0 METHODOLOGY

2.1 Sample Origin

The majority of non-clay minerals used in this report were obtained from Ward's Natural Science Establishment, Rochester, New York; the Burnham Mineral Company (Burminco), Monrovia, California; or from an in-house collection. Most of the clay minerals were obtained from the Source Clay Mineral Repository, University of Missouri, Columbia, Missouri. In all cases, the supplier of the sample is listed in the ancillary information describing each sample.

It was not possible to obtain sufficiently large quantities of all natural minerals, particularly oxides and some clays. In these cases, synthetic minerals were used. In all cases, XRD data for the synthetic mineral agreed with the data reported for the natural mineral in the Mineral Powder Diffraction File Data Book (Joint Committee Powder Diffraction Standards, 1980).

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2.2 Sample Preparation

Mineral samples were pulverized with a steel percussion mortar. A magnet was used to remove metallic impurities introduced during this procedure. The pulverized sample was then ground with mortar and pestle and separated into different size fractions by wet-sieving with distilled water or 2-propanol (for water-soluble minerals) in nested sieves. The size fractions selected for reflectance measurements were 125-500µm, 45-125µm, and <45µm, which correspond to fine-to-medium sand, coarse silt to very fine sand, and medium silt to clay, respectively. In certain instances, only one grain size was analyzed due to the nature and/or paucity of the sample (e.g., cristobalite, clay minerals).

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2.3 X-ray Diffraction

The purity of each mineral sample was evaluated by using standard XRD methods described in Klug and Alexander (1954). A Norelco water-cooled X-ray diffractometer, equipped with a vertical scan goniometer and focusing monochromater was used for the analysis. All samples were analyzed by Ni-filtered, CuK radiation. Diffraction lines were recorded on a strip chart recorder at a scan rate of 1o (2 ) per minute over the angular range of 4o to 65o (2 ).

The Mineral Powder Diffraction File Search Manual and Data Book (Joint Committee on Powder Diffraction Standards, 1980) was used to identify crystalline phases. Additional XRD data were obtained from Borg and Smith (1969) and Berry and Thompson (1962). Identification of clay mineral phases was facilitated by techniques and diffraction data presented by Carroll (1970) and Brindley and Brown (1980).

The XRD criteria used to determine the purity of our samples were based on the number and intensity of diagnostic peaks. If impurities were identified in a sample, a semiquantitative estimate of their abundance was made by XRD. Several limitations of XRD analysis are applicable to our results. Many crystalline substances are strong diffractors of X-rays and can be detected when present in concentrations as small as 1-2 percent. Other materials diffract X-rays less efficiently and yield diffraction patterns of measurable intensity only when they constitute a major portion of the sample. As a result, certain minor constituents cannot be identified by XRD alone. For example, many of the feldspars have suffered minor incipient alteration, which manifests as small features in the Beckman spectra (for example, the sharp feature around 2.2µm in Sanidine TS-14A). No alteration products were identified by XRD in the Sanidine sample. The problems associated with the detection limits of XRD analyses are discussed in detail in Klug and Alexander (1954).

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2.4 Electron Microprobe

Chemical composition data were acquired by electron microprobe analysis for some of our minerals known to deviate significantly from idealized end-member compositions. These analyses were undertaken with the Cameca CAMEBAX electron microprobe at U.C.L.A. Chemical compositions were obtained from polished grain mounts in the wavelength dispersive mode by using 15 keV accelerating potential, 1.5 nAo absorbed current and 20s counting intervals. Compositionally well-characterized silicate minerals from the U.C.L.A. collection were employed as standards. Raw data were reduced according to the ZAF correction scheme (Henog et al., 1982). Results for major elements are believed to be accurate to ±1%. Quantitative chemical compositions presented for minerals in Appendix B represent the average of three or more individual analyses and are indicated by an asterisk (*) following the chemical formula.

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2.5 Spectrophotometer

Hemispherical reflectance measurements in the visible and short-wavelength region of the electromagnetic spectrum (0.4 to 2.5µm) were made by using a Beckman UV5240 spectrophotometer (Price, 1977). The Beckman UV5240 incorporates a single-pass monochromator and utilizes a diffraction grating as its dispersing element. The sampling interval is .001µm, from 0.4 to 0.8µm, and .004µm, from 0.8 to 2.5µm. Our instrument has been modified with an integrating sphere rotated 90 degrees, which facilitates measurement of powdered samples and soils by allowing the materials to remain in the sample holder in a horizontal position.

For reflectance measurements, the size-sorted samples were poured into aluminum sample holders that measured 3.2 cm in diameter and 0.5 cm in depth. The upper surface was carefully smoothed with the edge of a stainless steel spatula. Smoothing with a spatula may compact the sample and introduce some preferred orientation of grains. However, every effort was made to minimize these effects. The sample was then placed in the sample compartment where it and a Halon reference standard were illuminated alternately by monochromatic radiation from a high-intensity halogen source lamp. Halon, a trade name for polytetrafluoroethylene powder, has been shown to be a good diffuser of incident radiation over the spectral range of the 0.2 - 2.5 m region (Weidner and Hsia, 1981). However, Halon does have a small absorption feature near 2.2µm. This feature is manifest in spectra with a high reflectance in the 2.0 - 2.5µm region. In order to correct this Halon artifact, the spectra were multiplied by the reflectance of Halon vs a perfect diffuser given in Weidner and Hsia (1981). The correction largely removed the influence of the Halon absorption feature in our spectra.

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3.0 References

Adams, J. B. (1967), Lunar surface composition and particle size: implication from laboratory and lunar spectral reflectance data, J. Geophys. Res., 72, 5717-5720.

Adams, J. B., and A. L. Filice (1967), Spectral reflectance 0.4 to 2.0 µm of silicate rock powders, J. Geophys. Res., 72, 5705-5715.

Adams, J. B. (1974), Visible and near-infrared diffuse reflectance spectra of pyroxenes as applied to remote sensing of solid objects in the solar system, J. Geophys. Res., 79, 4829-4836.

Adams, J. B. (1975), Interpretation of visible and near-infrared diffuse reflectance spectra of pyroxenes and other rock forming minerals, in Infrared and Raman Spectroscopy of Lunar and Terrestrial Materials (C. Karr, ed.), Academic, New York, 91-116.

Berry, L. G., and R. M. Thompson (1962), X-ray powder data for ore minerals: the Peacock atlas, Geol. Soc. of Am. Memoir, 85.

Borg, I. Y., and D. K. Smith (1969), Calculated X-ray powder patterns for silicate minerals, Geol. Soc. of Am. Memoir, 122.

Brindley, G. W., and G. Brown, eds. (1980), Crystal structures of clay minerals and their X-ray identification, London, Mineralogical Society, Monograph, 5.

Carroll, D. (1970), Clay minerals: a guide to their X-ray identification, Geol. Soc. of Am. Special Paper, 126.

Clark, R. N., and T. L. Roush (1984), Reflectance spectroscopy: quantitative analysis techniques for remote sensing applications, J. Geophys. Res., 89, No. B-7, 6329- 6340.

Clark, R. N., T. V. V. King, M. Klejwa, G. A. Swayze, and N. Vergo (1990), High spectral resolution reflectance spectroscopy of minerals, J. Geophys. Res., 95, No. B-8, 12653-12680.

Crowley, J. K. (1986), Visible and near-infrared spectra of carbonate rocks: Reflectance variations related to petrographic texture and impurites, J. Geophys. Res., 91, No. B5, 5001-5012.

Fleischer, M. (1983), Glossary of mineral species 1983, Tucson, Mineralogical Record, Inc.

Gaffey, S. J. (1986), Spectral reflectance of carbonate minerals in the visible and near infrared (0.35-2.55µm): Calcite, Aragonite and Dolomite, American Mineralogist, 71, 151-162. Green, A. A., and M. D. Craig (1985), Analysis of aircraft spectrometer data with logarithmic residuals, Proc. of the Airborne Imaging Spectrometer Data Analysis Workshop, Jet Propulsion Laboratory Publication 85-41, Jet Propulsion Laboratory, Pasadena, California, U.S.A., April 8-10, 1985, 111-119.

GSFC (1991), The Pilot Land Data System, PLDS User Guide: unpublished Document, Goddard Space Flight Center.

Hauff, P., and Kruse, F. (1990), I.G.C.P. International Spectral Properties Database. Center for the Study of the Earth from Space, Boulder, Colorado - Preliminary version.

Henog, J., and Maurice, F. (1982), Practical Quantitative Analysis of Bulk Specimens: in Microanalysis Scanning Electron Microscopy, Maurice, F., May, L., and Tivier, R., Eds. (France), 238-281.

Hunt, G. R. (1977), Spectral signatures of particulate minerals in the visible and near- infrared, Geophysics, 42, No 3, 501-513.

Hunt, G. R., and J. W. Salisbury (1970), Visible and near-infrared spectra of minerals and rocks, I. Silicate minerals, Mod. Geol., 1, 283-300.

Hunt, G. R., and J. W. Salisbury (1971), Visible and near-infrared spectra of minerals and rocks, II. Carbonates, Mod. Geol., 2, 23-30.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1971), Visible and near-infrared spectra of minerals and rocks, III. Oxides and hydroxides, Mod. Geol., 2, 195-205.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1971), Visible and near-infrared spectra of minerals and rocks, IV. Sulphides and sulphates, Mod. Geol., 3, 1-14.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1972), Visible and near-infrared spectra of minerals and rocks, V. Halides, arsenates, vanadates, and borates, Mod. Geol., 3, 121-132.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1973), Visible and near-infrared spectra of minerals and rocks, VI. Additional silicates, Mod. Geol., 4, 85-106.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1973), Visible and near-infrared spectra of minerals and rocks, VII. Acidic igneous rocks, Mod. Geol., 4, 217-224.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1973), Visible and near-infrared spectra of minerals and rocks, VIII. Intermediate igneous rocks, Mod. Geol., 4, 237-244.

Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1974), Visible and near-infrared spectra of minerals and rocks, IX. Basic and ultrabasic igneous rocks, Mod. Geol., 5, 15- 22. Hunt, G. R., J. W. Salisbury, and C. J. Lenhoff (1975), Visible and near-infrared spectra of minerals and rocks, X. Stony meteorites, Mod. Geol., 5, 115-126.

Hunt, G. R., and Salisbury, J. W. (1976), Visible and near-infrared spectra of minerals and rocks, XII. Metamorphic rocks, Mod. Geol., 5, 219-228.

Hunt, G. R., and Salisbury, J. W. (1976), Visible and near-infrared spectra of minerals and rocks, XI. Sedimentary rocks. Mod. Geol. 5, 211-217.

Hunt, G. R. (1977), Spectral signatures of particulate minerals in the visible and near- infrared. Geophysics, 42, No. 3, 501-513.

Hunt, G. R. (1979), Near-infrared (1.3-2.4µm) spectra of alteration minerals - potential for use in remote sensing, Geophysics, 44, No. 12, 1974-1986.

Hurlbut, C. S., Jr., and C. Klein (1977), Manual of mineralogy (after James D. Dana), 19th ed., John Wiley & Sons, Inc., New York.

J.C.P.D.S. (1980), Mineral powder diffraction file search manual and data book, 1601 Park Lane, Swarthmore, Pennsylvania.

Klug, H. P., and L. E. Alexander (1954), X-ray diffraction procedures for polycrystalline and amorphous materials, John Wiley & Sons, Inc., New York.

Krohn, M. D., and Altaner, S. P. (1987), Near-infrared detection of ammonium minerals, Geophysics, 52, No. 7, 924-930.

Lang, H. R., Bartholomew, M. J., Grove, C. I., and Paylor, E. D. (1990), Spectral reflectance characterization (0.4-2.5 and 8.0 to 12µm) of Phanerozoic strata, Wind River Basin and Southern Bighorn Basin Area, Wyoming, J. Sed. Pet., 60, No. 4, 504-524.

Lindberg, J. D., and Snyder, D. G. (1972), Diffuse reflectance spectra of several clay minerals: American Mineralogist, 57, 485-493.

Phillips, W. R., and D. T. Griffen (1981), Optical mineralogy: the non-opaque minerals, W. H. Freeman and Co., San Francisco.

Price, A. (1977), Beckman Instructions 015-555416, Fullerton, California.

Weidner, V. R., and J. J. Hsia (1981), Reflection properties of pressed polytetrafluoro- ethylene powder, J. Opt. Soc. Am., 71, 856-861.

Wendlandt, W. W., and Hecht, H. G. (1966), Reflectance Spectroscopy: John Wiley and Sons, New York.

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