The U. S. Geological Survey, Digital Spectral Library: Version 1 (0.2 to 3.0µm)

Roger N. Clark1, Gregg A. Swayze1, Andrea J. Gallagher1
Trude V.V. King1, and Wendy M. Calvin2

U.S. Geological Survey, Open File Report 93-592


1326 Pages
499 Figures
5 Tables

1 U.S. Geological Survey, MS 964
Box 25046 Federal Center
Denver, CO 80225-0046

2 U.S. Geological Survey
2255 N. Gemini Dr.
Flagstaff, AZ 86001

For further information, contact :

Roger N. Clark at (303) 236-1332 (office)
(303) 236-1425 (FAX) (Internet mail)

(Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey.)


|Sample Documentation|
|Sample Naming |
|The Digital Data File|
|Table 1: Spectral Library Entries|
|Table 2: Minerals by Group |
|Table 3: Spectral Entries by Type|
|Table 4: Sample Listing of Splib04a |
|Table 5: Specpr Format Digital Spectral Lib. |



Spectral Library Entries

(The Table below gives the page numbers for the hard-copy version. To get spectral plots online with sample descriptions, clisk here. )
Mineral Page Number
Acmite NMNH133746 Pyroxene A1
Actinolite HS116 A4
Actinolite HS22 A7
Actinolite HS315 A10
Actinolite NMNH80714 A13
Actinolite NMNHR16485 A16
Adularia GDS57 (Orthoclase) A19
Albite GDS30 Plagioclase A22
Albite HS324 Plagioclase A25
Albite HS66 Plagioclase A28
Allanite HS293 A31
Almandine HS114 Garnet A34
Almandine WS475 Garnet A37
Almadine WS476 Garnet A40
Almandine WS477 Garnet A43
Almandine WS478 Garnet A46
Almandine WS479 Garnet A49
Alunite GDS84 (K) A52
Alunite GDS83 (Na) A55
Alunite GDS82 (Natroalunite) A58
Alunite AL706 A61
Alunite HS295 A63
Alunite SUSTDA-20 A66
Ammonioalunite NMNH145596 A68
Ammonium_Chloride GDS77 A70
Ammonio-jarosite SCR-NHJ A72
Ammonio-Illite/Smectite GDS87 A74
Ammonio-Smectite GDS86 (Sy) A76
Amphibole NMNH78662 A78
Analcime GDS1 Zeolite A81
Andalusite NMNHR17898 A84
Andesine HS142 Plagioclase A87
Andradite GDS12 Garnet A90
Andradite HS111 Garnet A93
Andradite NMNH113829 Garnet A96
Andradite WS487 Garnet A99
Andradite WS488 Garnet A102
Anhydrite GDS42 A105
Annite WS660 Biotite A108
Annite WS661 Biotite A111
Anorthite GDS28 Plagioclase A114
Anorthite HS201 Plagioclase A117
Anorthite HS349 Plagioclase A119
Anthophyllite HS286 A122
Antigorite NMNH96917 A125
Antigorite NMNH17958 A133
Arsenopyrite HS262 A136
Augite NMNH120049 A139
Augite WS588 Pyroxene A142
Augite WS592 Pyroxene A144
Axinite HS342 A146
Azurite WS316 A149
Barite HS79 B1
Bassanite GDS145 B4
Beryl GDS9 B6
Beryl HS180 B9
Biotite HS28 B12
Bloedite GDS147 B15
Bronzite HS9 Pyroxene B17
Brookite HS443 B20
Brucite HS247 B22
Buddingtonite GDS85 D-206 B25
Buddingtonite NHB2301 B28
Butlerite GDS25 B31
Bytownite HS106 Plagioclase B34
Calcite WS272 C1
Calcite HS48 C4
Calcite CO2004 C7
Carbon_Black GDS68 C10
Carnallite NMNH98011 C13
Carnallite HS430 C15
Cassiterite HS279 C18
Celestite HS251 Barite C21
Celsian HS200 C24
Chabazite HS193 C27
Chalcedony CU91-6A C30
Chalcopyrite HS431 C32
Chalcopyrite S26-36 C35
Chert ANP90-6D C38
Chlorapatite WS423 C40
Chlorite HS179 C43
Chlorite SMR-13 Mg C46
Chromite HS281 C53
Chrysocolla HS297 C56
Chrysotile HS323 C59
Cinnabar HS133 C62
Clinochlore NMNH83369 C65
Clinochlore_Fe GDS157 Chlorite C68
Clinochlore GDS158 Chlorite C71
Clinochlore GDS159 Chlorite C74
Clinochlore_Fe SC-CCa-1 C77
Clinoptilolite GDS2 Zeolite C82
Clinoptilolite GDS152 Zeolite C85
Clinozoisite HS299 C87
Clintonite NMNH126553 C90
Cobaltite HS264 C93
Colemanite GDS143 C96
Cookeite CAr-1 C98
Copiapite GDS21 C103
Coquimbite GDS22 C106
Cordierite HS346 C108
Corrensite CorWa-1 C111
Corundum HS283 C114
Covellite HS477 C117
Cronstedtite M3542 C119
Cummingtonite HS294 C121
Cuprite HS127 C124
Datolite HS442 D1
Datolite SU51399 D4
Desert_Varnish GDS141 (Entrada) D7
Desert_Varnish GDS78A D9
Desert_Varnish ANP90-14 D12
Diaspore HS416 D14
Dickite NMNH106242 D17
Dickite NMNH46967 D19
Diopside HS317 (Cr) Pyroxene D21
Diopside HS15 Pyroxene D24
Diopside NMNHR18685 D27
Dipyre BM1959,505 Scapolite D30
Dolomite HS102 D33
Dolomite COD2005 D36
Dumortierite HS190 D39
Elbaite NMNH94217-1 E1
Endellite GDS16 E6
Enstatite NMNH128288 Pyroxene E9
Epidote GDS26 E12
Epidote HS328 E17
Epsomite GDS149 (Hexahydrite) E20
Erionite+Offretite GDS72 E22
Erionite+Merlinoite GDS144 E25
Eugsterite GDS140 E27
Europium_Oxide GDS33 E29
Fassaite HS118 Pyroxene F1
Ferrihydrite GDS75 Sy F4
Fluorapatite WS416 F6
Galena HS37 G1
Galena S102-17 G4
Galena S102-1B G8
Galena S105-2 G12
Galena S26-39 G16
Galena S26-40 G20
Gaylussite NMNH102876-2 G24
Gibbsite HS423 G27
Gibbsite WS214 G30
Glauconite HS313 G33
Glaucophane HS426 G36
Goethite WS222 G39
Goethite HS36 G42
Goethite WS219 (Limonite) G45
Goethite WS220 G48
Grossular HS113 Garnet G51
Grossular NMNH155371 Garnet G54
Grossular WS485 Garnet G57
Grossular WS483 Garnet G60
Grossular WS484 Garnet G63
Gypsum HS333 (Selenite) G66
Gypsum SU2202 G69
H2O-Ice GDS136 H1
Halite HS433 H4
Halloysite NMNH106236 H7
Halloysite NMNH106237 H9
Halloysite CM13 H12
Halloysite KLH503 H15
Halloysite+Kaolinite CM29 H18
Hectorite SHCa-1 H21
Hedenbergite NMNH119197 H25
Hedenbergite HS10 H27
Hematite=2%+98%Qtz GDS76 H30
Hematite GDS27 H32
Hematite GDS69 H35
Hematite HS45 H44
Hematite WS161 H47
Hematite FE2602 H50
Heulandite GDS3 Zeolite H53
Heulandite NMNH84534 Zeolite H56
Holmquistite HS291 Amphibole H58
Hornblende_Mg NMNH117329 H61
Hornblende_Fe HS115 Amphibole H63
Hornblende HS16 H66
Hornblende HS177 H69
Howlite GDS155 H72
Hydrogrossular NMNH120555 H75
Hydroxyl-Apatite WS425 H78
Hypersthene NMNHC2368 H81
Hypersthene PYX02 Pyroxene H84
Illite GDS4 I1
Illite IMt-1 I4
Illite IL101 I8
Illite IL105 I10
Ilmenite HS231 I12
Jadeite HS343 J1
Jarosite GDS99 (K, Sy) J4
Jarosite GDS98 (K, Sy) J7
Jarosite GDS100 (Na, Sy) J10
Jarosite GDS101 (Na, Sy) J13
Jarosite GDS24 Na J16
Jarosite JR2501 (K) J19
Jarosite NMNH95074-1 (Na) J21
Jarosite WS368 (Pb) J23
Jarosite SJ-1 (H3O,10-20%) J26
Kainite NMNH83904 K1
Kaolinite CM9 K4
Kaolinite KGa-1 K7
Kaolinite KGa-2 K10
Kaolinite KL502 K13
Kaolinite GDS11 K16
Kaolinite CM3 K19
Kaolinite CM5 K22
Kaolinite CM7 K25
Kaolin/Smectite KLF506 K28
Kaolin/Smectite KLF508 K31
Kaolin/Smectite H89-FR-2 K34
Kaolin/Smectite H89-FR-5 K37
Kaolin/Smectite KLF511 K40
Kerogen BK-Cornell K43
Labradorite HS105 Plagioclase L1
Labradorite HS17 L4
Laumontite GDS5 Zeolite L7
Lazurite HS418 L9
Lepidocrosite GDS80 (Sy) L11
Lepidolite HS167 L14
Lepidolite NMNH105538 L17
Lepidolite NMNH105543 L19
Lepidolite NMNH88526-1 L21
Lepidolite NMNH105541 L23
Limonite HS41 L25
Lizardite NMNHR4687 L28
Maghemite GDS81 Sy M1
Magnesite+Hydromagnesite HS47 M4
Magnetite HS195 M7
Magnetite HS78 M10
Malachite HS254 M13
Manganite HS138 M16
Margarite GDS106 M18
Marialite NMNH126018-2 M20
Mascagnite GDS65 Ammon Sulfate M23
Meionite WS700 M27
Meionite WS701 M30
Mesolite+Hydroxyapophyll. GDS6 M33
Microcline HS82 M35
Microcline HS103 Feldspar M38
Microcline HS107 Feldspar M41
Microcline HS108 Feldspar M44
Microcline HS151 Feldspar M47
Microcline NMNH135231 M50
Mirabilite GDS150 M52
Mizzonite NMNH113775-1 M55
Mizzonite BM1931,12 Scapolite M58
Mizzonite HS350 Scapolite M61
Mizzonite HS351 Scapolite M64
Monazite HS255 M67
Monticellite HS339 M70
Montmorillonite SWy-1 M73
Montmorillonite SAz-1 M76
Montmorillonite SCa-2 M79
Montmorillonite CM27 M83
Montmorillonite CM20 M86
Montmorillonite CM26 M89
Montmorillonite STx-1 M92
Montmorillonite+Illite CM37 M95
Montmorillonite+Illite CM42 M98
Mordenite GDS18 M101
Mordenite+Clinopt. GDS151 M103
Muscovite GDS107 M105
Muscovite GDS108 M107
Muscovite GDS111 M110
Muscovite GDS113 M113
Muscovite GDS114 M116
Muscovite GDS116 M119
Muscovite GDS117 M122
Muscovite GDS118 M125
Muscovite GDS119 M128
Muscovite GDS120 M131
Muscovite HS146 M134
Muscovite HS24 M137
Muscovite IL107 M140
Nacrite GDS88 N1
Natrolite HS169 N4
Natrolite+Zeolites HS168 N7
Natrolite NMNH83380 Zeolite N10
Neodymium_Oxide GDS34 N12
Nepheline HS19 N15
Nephrite HS296 Amphibole N18
Niter GDS43 N21
Nontronite GDS41 N23
Nontronite NG-1 N26
Nontronite SWa-1 N30
Oligoclase HS110 Plagioclase O1
Oligoclase HS143 Plagioclase O4
Olivine NMNH137044 Fo92 O6
Olivine GDS70 Fo89 O10
Olivine HS285 Fo80 O16
Olivine HS420 O19
Olivine KI3005 Fo11 O22
Olivine KI3054 Fo66 O25
Olivine KI3188 Fo51 O28
Olivine KI3189 Fo60 O31
Olivine KI3291 Fo29 O34
Olivine KI3377 Fo18 O37
Olivine KI4143 Fo41 O40
Olivine GDS71 Fo91 O43
Opal WS732 O47
Opal (Hyalite) TM8896 O49
Orthoclase NMNH113188 O52
Orthoclase NMNH142137 O54
Orthoclase HS13 O56
Palygorskite CM46 Attapulgite P1
Palygorskite PFL-1 Attapulgite P4
Paragonite GDS109 P6
Pectolite NMNH94865 P9
Perthite HS415 P13
Phlogopite GDS20 P16
Phlogopite HS23 P19
Phlogopite WS496 P22
Phlogopite WS675 P25
Pigeonite HS199 P27
Pinnoite NMNH123943 P30
Pitch_Limonite GDS104 P33
Polyhalite NMNH92669-4 P35
Praseodymium_Oxide GDS35 P37
Prochlorite SMR-14 P40
Psilomelane HS139 P45
Pyrite HS35 P48
Pyrite S142-1 P51
Pyrite S26-8 P54
Pyrite S29-4 P57
Pyrite S30 P60
Pyrope WS474 P63
Pyrophyllite PYS1A P66
Pyrophyllite SU1421 P70
Pyroxene HS119 P72
Pyrrhotite HS269 P75
Quartz HS117 Aventurine Q1
Quartz GDS31 Q4
Quartz HS32 Q7
Quartz GDS74 (Sand) Ottawa Q10
Rectorite ISR202 R1
Rectorite RAr-1 R4
Rhodochrosite HS338 R7
Rhodochrosite HS67 R9
Rhodonite NMNHC6148 R12
Rhodonite HS325 R15
Richterite HS336 Amphibole R18
Richterite NMNH150800 Amphibole R21
Riebeckite NMHN122689 Amphibole R24
Riebeckite HS326 Amphibole R27
Rivadavite NMNH170164 R30
Roscoelite EN124 R33
Rutile HS126 R36
Rutile HS137 R39
Samarium_Oxide GDS36 S1
Sanidine GDS19 Feldspar S4
Sanidine NMNH103200 Feldspar S7
Saponite SapCa-1 S10
Sauconite GDS135 S14
Scolecite GDS7 Zeolite S16
Sepiolite SepNev-1 S18
Sepiolite SepSp-1 S22
Serpentine HS318 S26
Serpentine HS8 S29
Siderite HS271 S32
Siderophyllite NMNH104998 S35
Sillimanite HS186 S38
Smaragdite HS290 Amphibole S41
Sodium_Bicarbonate GDS55 S44
Spessartine NMNH14143 Garnet S46
Spessartine HS112 Garnet S49
Spessartine WS480 Garnet S52
Spessartine WS481 Garnet S54
Sphalerite HS136 S56
Sphalerite S102-7 S59
Sphalerite S102-8 S62
Sphalerite S26-34 S65
Sphalerite S26-35 S68
Sphene, Titanite HS189 S71
Spodumene HS210 S74
Staurolite HS188 S77
Stilbite GDS8 Zeolite S80
Stilbite HS482 Zeolite S82
Strontianite HS272 S84
Sulfur GDS94 S86
Syngenite GDS139 S88
Talc GDS23 T1
Talc HS21 T4
Talc WS659 T7
Talc TL2702 T10
Teepleite+Trona NMNH102798 T13
Tephroite HS419 Olivine T15
Thenardite GDS146 T18
Thenardite HS450 T21
Thuringite SMR-15 Chlorite T24
Tincalconite GDS142 T30
Topaz Wigwam_Area_A_#10 T33
Topaz Wigwam_Area_2_#12 T36
Topaz Wigwam_Area_3_#13 T39
Topaz Wigwam_Area_4_#14 T42
Topaz Wigwam_Area_5_#15 T45
Topaz Wigwam_Area_6_#16 T48
Topaz Harris_Park_#17 T51
Topaz Crystal_Park_#2 T54
Topaz Jos_#22 T57
Topaz Harris_Park_#3 T60
Topaz Tarryalls_#4 T63
Topaz Little_3_Mine_#41 T66
Topaz Cameron_Cone_#42 T69
Topaz Mt._Antero_#5 T72
Topaz Glen_Cove_#6 T75
Topaz Glen_Cove_#8 T78
Topaz Harris_Park_#9 T81
Topaz HS184 T84
Tourmaline HS282 T87
Tremolite HS18 T90
Tremolite NMNH117611 T93
Trona GDS148 T96
Ulexite HS441 U1
Ulexite GDS138 U4
Uralite HS345 U6
Uvarovite NMNH106661 Garnet U9
Vermiculite GDS13 V1
Vermiculite VTx-1 V3
Vermiculite WS681 V7
Vesuvianite HS446 Idocrase V9
Witherite HS273 W1
Wollastonite HS348 W4
Zincite+Franklinite HS147 Z1
Zircon WS522 Z4
Zoisite HS347 Z6
Aspen_Leaf-A DW92-2 PLANT1
Aspen_Leaf-B DW92-3 PLANT3
Blackbrush ANP92-9A PLANT5
Blue_Spruce DW92-5 PLANT7
Cheatgrass ANP92-11A PLANT9
Dry_Long_Grass AV87-2 (Brown) PLANT11
Fir_Tree IH91-2 PLANT13
Juniper_Bush IH91-4B PLANT15
Lawn_Grass GDS91 PLANT17
Maple_Leaves DW92-1 PLANT19
Pinon_Pine ANP92-14A PLANT21
Rabbitbrush ANP92-27 PLANT23
Russian_Olive DW92-4 PLANT25
Sage_Brush IH91-1B PLANT27
Saltbrush ANP92-31A PLANT29
Tumbleweed ANP92-2C PLANT31
Walnut_Leaf SUN PLANT33


We have developed a digital reflectance spectral library, with management and spectral analysis software. The library includes 498 spectra of 444 samples (some samples include a series of grain sizes) measured from approximately 0.2 to 3.0 µm . The spectral resolution (Full Width Half Maximum) of the reflectance data is <= 4 nm in the visible (0.2-0.8 µm) and <= 10 nm in the NIR (0.8-2.35 µm). All spectra were corrected to absolute reflectance using an NIST Halon standard. Library management software lets users search on parameters (e.g. chemical formulae, chemical analyses, purity of samples, mineral groups, etc.) as well as spectral features.

Minerals from borate, carbonate, chloride, element, halide, hydroxide, nitrate, oxide, phosphate, sulfate, sulfide, sulfosalt, and the silicate (cyclosilicate, inosilicate, nesosilicate, phyllosilicate, sorosilicate, and tectosilicate) classes are represented. X-Ray and chemical analyses are tabulated for many of the entries, and all samples have been evaluated for spectral purity. The library also contains end and intermediate members for the olivine, garnet, scapolite, montmorillonite, muscovite, jarosite, and alunite solid-solution series. We have included representative spectra of H2O ice, kerogen, ammonium-bearing minerals, rare-earth oxides, desert varnish coatings, kaolinite crystallinity series, kaolinite-smectite series, zeolite series, and an extensive evaporite series. Because of the importance of vegetation to climate-change studies we have include 17 spectra of tree leaves, bushes, and grasses.

The library and software are available as a series of U.S.G.S. Open File reports. PC user software is available to convert the binary data to ascii files (a separate U.S.G.S. open file report). Additionally, a binary data files are on line at the U.S.G.S. in Denver for anonymous ftp to users on the Internet. The library search software enables a user to search on documentation parameters as well as spectral features. The analysis system includes general spectral analysis routines, plotting packages, radiative transfer software for computing intimate mixtures, routines to derive optical constants from reflectance spectra, tools to analyze spectral features, and the capability to access imaging spectrometer data cubes for spectral analysis. Users may build customized libraries (at specific wavelengths and spectral resolution) for their own instruments using the library software.

We are currently extending spectral coverage to 150 µm. The libraries (original and convolved) will be made available in the future on a CD-ROM.


Analysis of spectroscopic data from the laboratory, from aircraft, and from spacecraft requires a knowledge base. The spectral library discussed here forms a knowledge base for the spectroscopy of minerals and related materials of importance to a variety of research programs being conducted at the U. S. Geological Survey. Much of this library grew out of the need for spectra to support imaging spectroscopy studies of the Earth and Planets.

Imaging spectrometers, such as the Airborne Visible/Infra-Red Imaging Spectrometer (AVIRIS), have narrow band widths in many contiguous spectral channels that permit accurate definition of absorption features from a variety of materials. Identification of materials from such data requires a knowledge base: a comprehensive spectral library of minerals, vegetation, man-made materials, and other subjects in the scene.

Our research involves the use of the spectral library to identify the components in a spectrum of an unknown. Therefore, the quality of the library must be very good. However, the quality required in a spectral library to successfully perform an investigation depends on the scientific questions to be answered and the type of algorithms to be used. For example, to map a mineral using imaging spectroscopy and the Clark et al. (1990) mapping algorithm, one simply needs a diagnostic absorption band. Such a feature can be obtained from a spectrum of a sample containing large amounts of contaminants, including those that add other spectral features, as long as the shape of diagnostic feature of interest is not modified. If, however, the data are needed for radiative transfer models to derive mineral abundances from reflectance spectra, then completely uncontaminated spectra are required. This library contains spectra that span a range of quality, with purity indicators to flag spectra for (or against) particular uses.

Acquiring spectral measurements and sample characterizations for this library has taken about 8 years. This first release contains 498 spectra of 444 samples. Software to manage the library and provide scientific analysis capability is also provided (Clark, 1980, 1993, Gorelick and Clark, 1993). A personal computer (PC) reader for the library is also available (Livo et al., 1993).

This document describes the contents of the library and presents a paper copy of the spectra in the form of plots and written text showing the documentation. The intent of the paper copy is as a reference document. You can look up specific documentation, or examine and compare plots of various spectra. It is not intended to be completely cross referenced and easily searchable--that is what computers are for. This paper copy is a print-out of the digital data set. However, this is a digital spectral library; searches for spectra and information should be carried out with the aid of a computer and not on the paper copy. The section on availability describes the details for obtaining digital data.


In our view, an ideal spectral library consists of pure samples, covering a very wide range of materials, a large wavelength range with very high precision, and sample analysis and documentation to establish the quality of the spectra. Budgets, time, and available equipment limit what can be achieved.

Ideally, for minerals, the sample analysis would include X-ray diffraction (XRD), electron microprobe (EM) or X-ray Fluorescence (XRF), and petrographic microscopic analyses. For some minerals, like iron oxides, additional analyses, such as Mossbauer, would be helpful. We have found that to make the basic spectral measurements, provide XRD, EM or XRF, microscopic analysis, document the results, and complete an entry of one spectral library sample, takes about one person-week. Additional spectra of the same sample (e.g. a grain size series) increases the time, but usually not an additional week per spectrum, but more like 0.5 day per spectrum (mostly sample preparation). We had hoped as our experience increased this time would decrease, but it did not.

Thus an ideal spectral library with 498 spectra of 444 samples would take on the order of 444 person-weeks, or about 8.9 person-years. Our budgets and time commitment have not allowed this level of effort, so this release of the library does not have all samples completely characterized. We estimate, however, that this release represents about 7.5 person-years of effort. The characterization of samples will continue as our budgets allow, and results will be added in future releases of the database. Latest updates on the characterization (e.g. new XRD analyses and spectral purity revisions) will be kept online for anonymous ftp on the Internet.

The ideal spectral coverage depends on the desired research. This release covers the range 0.2 to 3.0 µm. Future releases will include coverage to 150 µm for many of the samples listed here.


The spectral library contains spectra of 423 minerals, 17 plants and some miscellaneous materials (Table 1, 2, and 3). In some cases, several spectra were measured to span a solid solution series and/or a grain size series. We tried to include spectra of all mineral classes, particularly those important to imaging spectroscopy remote sensing. In other cases, we have studied particular solid solution series because we are mapping them in the field with imaging spectroscopy or studying that mineral in detail. This explains, for example, why there are so many alunite, olivine, and topaz samples in the database. Future releases of the database will likely include additional spectra of solid solution series.

All spectra were run on a modified Beckman 5270 spectrometer (Clark et al., 1990b) from 0.2 to 3.0 µm and corrected to absolute reflectance. They were run with a signal-to-noise of at least 500 at a reference reflectance level of 1.0. A few minerals were also run over a slightly smaller wavelength range because of sample size limitations. For example, small sample quantities, necessary for purity, were measured using apertures in the beam to restrict the spot size of the spectrometer. This reduced light made integration times longer and the achievable range was sometimes reduced, typically to 0.3 to 2.7 µm. This also, in some cases, limited the signal to noise that was achievable. It is not possible with the current instrumentation to substantially improve the spectral data on small volume samples. The ice sample, measured at 77K, only includes the infrared range, 0.8 to 3.0 µm.


Each sample has a text entry describing the mineral, its composition, its formula, sample description, and pointers to corresponding spectra in the digital data file. The text entry is coded by keywords for computer program searching. Each spectrum has a pointer to the documentation, so that all related data are properly cross-referenced and can be found by a computer program as well as manually.

The sample documentation is organized by keyword so that it is computer readable. The program spsearch (Gorelick and Clark, 1993) may be used to search entries in the database. With this software, it is possible to do searches such as: show me all the entries whose sample formulae have OH (hydroxyl), whose compositions contain from 20 to 30% SiO2, and have a 2.2-µm band in their spectra.

The sample documentation includes extensive analyses such as X-ray diffraction, electron microprobe or XRF, X-ray fluorescence, and petrographic microscope examination. Not all analyses have been completed for all samples, but most samples have at least one analysis.


The mineral name for each sample occurs in 3 places: 1) the specpr title field for the spectrum, 2) the specpr title field for the description entry, and 3) after the "MINERAL:" keyword in the description. We have tried to use only proper mineral names as given in Fleischer 1980, and Klein and Hurlbut, 1985. Some users of the library may be unfamiliar with all the mineral names. For example, if you want to find all scapolites, you would have to know that Dipyre was a scapolite if you only looked at the specpr title fields. Because of the 40 character limit in a specpr title field, we could not include all common names there. However, use the "MINERAL:" keyword in the description for each sample. Here you could search for scapolite and you would find all entries in the "scapolite group" (Dipyre, Marialite, Meionite, and Mizzonite).

We have used specific mineral names except in a few cases where we still do not have sufficient data. For example, technically, there is no "hornblende," only ferro-hornblende and magnesio-hornblende. We have two samples where we can't make the distinction, so they are labeled hornblende.


The digital spectral library data are all included in one file in "specpr" format (see Clark, 1993). This file, splib04a, has been assembled and managed using specpr and is 8.2 megabytes in size (3.9 megabytes when compressed with the Unix compress command). The data are in IEEE binary floating point format. The entire library is assembled, plotted and printed by command files consisting of 1300 Unix shell commands, which in turn generate an additional 100 Unix shell commands which generate about 44,000 specpr commands plus about 6000 specpr commands for each instrument convolved library.

Specpr runs on Unix workstations. If the binary file is read on an IBM-PC compatible machine, the floating point numbers need their bytes swapped (this is done in the Livo et al., 1993 program). An ascii version is 15.8 megabytes uncompressed, or about 5.4 megabytes when compressed with the unix compress command.

The organization of the binary data file, in the form of a specpr listing, is shown in Table 4. The listing shows the record number, title, length of the data set (number of channels for spectra; number of bytes for text), and the time and date of data acquisition. Record 6 contains the wavelength set for the spectra, and record 8 contains the the spectral resolution data set. The resolution is shown in Figure 1. Entries with the keyword "DESCRIPT" are sample description records, and contain all the sample documentation. After the DESCRIPT are (usually) two empty records (title ..) for future expansion of the description. Next comes the reflectance data, with the keyword "ABS REF." The identifier "W1R1Bx," which signifies the wavelength range, resolution, spectrometer, and spectral purity which is described below (the "x" is a lower case spectral purity letter code). This release of the spectral library has only one spectral region (W1), resolution (R1) and spectrometer (B). After the reflectance record is the "errors to previous data" record. These are the standard deviation of the mean for each reflectance value. The next record in the listing contains the feature analysis for the spectrum. This feature analysis was done using the specpr f45 special function and is described in Clark et al. (1987), Clark (1993).

In the spectral library, any value of -1.23x1034 is considered a deleted point. Because of the inherent floating point inaccuracies of single precision numbers on various computers, values in the range -1.23001x1034 to -1.22999x1034 should be considered deleted points.

Table 1: Spectral Library Entries


Nr.of Samples Mineral Nr.of Samples Mineral Nr. of Samples Mineral
1 Acmite 1 Elbaite 2 Oligoclase
5 Actinolite 1 Endellite 12Olivine
1 Adularia 1 Enstatite 2 Opal
3 Albite 2 Epidote 3 Orthoclase
1 Allanite 1 Epsomite 2 Palygorskite
6 Almandine 2 Erionite 1 Paragonite
6 Alunite 1 Eugsterite 1 Pectolite
1 Ammonioalunite 1 Europium 4 Phlogopite
1 Ammoniojarosite 1 Fassaite 1 Pigeonite
1 Ammonium_Chloride 1 Ferrihydrite 1 Pinnoite
1 Ammonium_Illite/Smectite 1 Ferro-Hornblende 1 Pitch
1 Ammonium_Smectite 2 Ferroan Clinochlore 1 Plumbojarosite
1 Amphibole 1 Fluorapatite 1 Polyhalite
1 Analcime 6 Galena 1 Praseodymium
1 Andalusite 1 Gaylussite 1Prochlorite
1 Andesine 2 Gibbsite 1Psilomelane
5 Andradite 1 Glauconite 5Pyrite
1 Anhydrite 1 Glaucophane 1Pyrope
2 Annite 4 Goethite 2Pyrophyllite
3 Anorthite 5 Grossular 1Pyrrhotite
1 Anthophyllite 2 Gypsum 4 Quartz
2 Antigorite 1 Halite 2Rectorite
1 Arsenopyrite 5 Halloysite 2Rhodochrosite
4 Augite 1 Hectorite 2Rhodonite
1 Axinite 2 Hedenbergite 2Richterite
1 Azurite 6 Hematite 2Riebeckite
1 Barite 2 Heulandite 1Rivadavite
1 Bassanite 1 Holmquistite 1 Roscoelite
2 Beryl 2 Hornblende 2 Rutile
1 Biotite 1 Howlite 1 Samarium
1 Bloedite 1 Hydrogrossular 2 Sanidine
1 Bronzite 1 Hydroxylapatite 1 Saponite
1 Brookite 2 Hypersthene 1Sauconite
1 Brucite 1 Ice (water) 1Scolecite
2 Buddingtonite 4 Illite 2 Sepiolite
1 Butlerite 1 Ilmenite 2Serpentine
1 Bytownite 1 Jadeite 1Siderite
3 Calcite 7 Jarosite 1Siderophyllite
1 Carbon 1 Kainite 1Sillimanite
2 Carnallite 8 Kaolinite 1Smaragdite
1 Carphosiderite 5 Kaolinite/Smectite1 Sodium
1 Cassiterite 2 Labradorite 4Spessartine
1 Celestite 1 Laumontite 5Sphalerite
1 Celsian 1 Lazurite 1Spodumene
1 Chabazite 1 Lepidocrosite 1Staurolite
1 Chalcedony 5 Lepidolite 2Stilbite
2 Chalcopyrite 1 Limonite 1Strontianite
1 Chert 1 Lizardite 1 Sulfur
1 Chlorapatite 1 Maghemite 1Syngenite
2 Chlorite 1 Magnesio-Hornblende 4Talc
1 Chromite 1 Magnesite 1Teepleite
1 Chrysocolla 2 Magnetite 1Tephroite
1 Chrysotile 1 Malachite 2Thenardite
1 Cinnabar 1 Manganite 1Thuringite
2 Clinochlore 1 Margarite 1Tincalconite
2 Clinoptilolite 1 Marialite 1Titanite
1 Clinozoisite 1 Mascagnite 18 Topaz
1 Clintonite 2 Meionite 1Tourmaline
1 Cobaltite 1 Mesolite 2Tremolite
1 Colemanite 1 Mg-Clinochlore 1Trona
1 Cookeite 7 Microcline 2 Ulexite
1 Copiapite 1 Mirabilite 1Uralite
1 Coquimbite 4 Mizzonite 1 Uvarovite
1 Cordierite 1 Monazite 3Vermiculite
1 Corrensite 1 Monticellite 1 Vesuvianite
1 Corundum 9 Montmorillonite 1Witherite
1 Covellite 1 Mordenite 1Wollastonite
1 Cronstedtite 1 Mordenite+Clinoptilolite 1Zincite
1 Cummingtonite 13 Muscovite 1 Zircon
1 Cuprite 1 Nacrite 1 Zoisite
2 Datolite 3 Natrolite
1 Diaspore 1 Neodymium
2 Dickite 1 Nepheline Other:
3 Diopside 1 Nephrite 3Desert_Varnish
1 Dipyre 1 Niter 1 Kerogen
2 Dolomite 3 Nontronite 17 Plants
1 Dumortierite


Table 2: Minerals in the Spectral Library by Group


Nr.of Minerals Mineral GroupNr.of Minerals Mineral Group
16 Alunite group 22 Garnet group
21 Amphibole group 8 Hematite group
3 Apatite group 23 Kaolinite-Serpentine group
2 Aragonite group 30 Mica group
1 Arsenopyrite group 17 Montmorillonite group
1 Axinite group 1 Nepheline group
2 Barite group 13 Olivine group
5 Calcite group 5 Pyrite group
2 Chalcopyrite group 16 Pyroxene group
9 Chlorite group 2 Rutile group
1 Cobaltite group 8 Scapolite group
1 Copiapite group 1 Sodalite group
2 Dolomite group 3 Spinel group
4 Epidote group 2 Tourmaline group
28 Feldspar group 16 Zeolite group


Table 3: Spectral Library Entries by Type

Nr.of Minerals Mineral Nr.of Other Other
1 Borate 3 Desert Varnish
21 Carbonate 1 Organic(Kerogen)
1 Chloride
7 Cyclosilicate
2 Element
4 Halide
13 Hydroxide 17 Plants:
45 Inosilicate
63 Nesosilicate 3 Grass
1 Nitrate 6 Shrub
24 Oxide 8 Tree
4 Phosphate
108 Phyllosilicate
5 Sorosilicate
33 Sulfate
23 Sulfide
2 Sulfosalt
64 Tectosilicate


Table 4: Sample Specpr Listing of the start of splib04a

Record Note or DateTitle Size
1 USGS Digital Spectral Library: splib04a 436 Characters of TEXT
2 **************************************** 41 Characters of TEXT
3 **************************************** 41Characters of TEXT
4 **************************************** 41Characters of TEXT
5 .. 41Characters of TEXT
6 USGS Denver Beckman STD wavelengths 1x 512 02:57:26.00 10/15/1985
8 USGS Denver Beckman STD resolution 1x 512 02:57:26.00 10/15/1985
10 ---------------------------------------- 41Characters of TEXT
11 Acmite NMNH133746 Pyroxene DESCRIPT 3136Characters of TEXT
14 .. 41Characters of TEXT
15 .. 41Characters of TEXT
16 Acmite NMNH133746 W1R1Ba ABS REF 480 15:18:47.00 03/23/1988
18 errors to previous data 480 15:18:47.00 03/23/1988
20 Acmite NMNH133746 W1R1Ba FEATANL 324 15:18:47.00 03/23/1988
22 ---------------------------------------- 41Characters of TEXT
23 Actinolite HS116 DESCRIPT 3367Characters of TEXT
26 .. 41Characters of TEXT
27 .. 41Characters of TEXT
28 Actinolite HS116.3B W1R1Bb ABS REF 480 08:41:01.00 07/11/1991
30 errors to previous data 480 08:41:01.00 07/11/1991
32 Actinolite HS116.3B W1R1Bb FEATANL 396 08:41:01.00 07/11/1991
34 ---------------------------------------- 41Characters of TEXT
35 Actinolite HS22 DESCRIPT 3130Characters of TEXT
38 .. 41Characters of TEXT
39 .. 41Characters of TEXT
40 Actinolite HS22.3B W1R1Bb ABS REF 480 12:06:59.00 03/16/1987
42 errors to previous data 480 12:06:59.00 03/16/1987
44 Actinolite HS22.3B W1R1Bb FEATANL 297 12:06:59.00 03/16/1987
46 ---------------------------------------- 41Characters of TEXT
47 Actinolite HS315 DESCRIPT 2913Characters of TEXT
49 .. 41Characters of TEXT
50 .. 41Characters of TEXT
51 Actinolite HS315.4B W1R1Bb ABS REF 480 11:47:02.00 10/31/1986
53 errors to previous data 480 11:47:02.00 10/31/1986
55 Actinolite HS315.4B W1R1Bb FEATANL 522 11:47:02.00 10/31/1986


Size is the number of data channels for spectra and FEATANL results

and number of bytes for text records.


Table 5: Specpr Format Digital Spectral Library Versions

splib04a master spectral library (Beckman range andresolution)

splib04b interpolated splib04a spectra to 950 channels for use in convolutions.

splib04c AVIRIS 1990 convolution 224 channels. (e.g. Cuprite)

splib04d AVIRIS 1990 convolution 208 channels

splib04e AVIRIS 1991 convolution 224 channels.

splib04f AVIRIS 1991 convolution 208 channels.

splib04g AVIRIS 1992 convolution 224 channels.

splib04h AVIRIS 1992 convolution 197 channels.

splib04i AVIRIS 1993 convolution 224 channels.

splib04j AVIRIS 1993 convolution 197 channels.

splib04k TM

splib04m Galileo NIMS

splib04n Cassini VIMS proposed

note: the letter l was skipped in the designation splib04_ to avoid confusion with the number 1.



Each spectrum has a purity code in its header. In this version of the spectral library, the code is: W1R1Bx The "W" stands for wavelength region followed by the region measured. All spectra in this version cover the nominal range of 0.2 to 3.0 µm which is region 1. The digital data for the wavelength set are located in splib04a, record 6.

The "R" stands for resolution, followed by the resolution index. All spectra in this version of the library were measured using resolution set 1 in wavelength region 1. Figure 1 shows the resolution function, and the digital data for the resolution are located in splib04a, record 8.

The next letter signifies the instrument used. All spectra in this version of the library were measured on the USGS, Denver Spectroscopy Laboratory, Beckman 5270 spectrometer, and are designated by the letter "B".

Following the instrument letter is a lower case letter signifying the spectral purity of the spectrum for this wavelength range and resolution (the "x" in the above example is one of the following letters).

a: The spectrum and sample are pure based on significant supporting data available to the authors. The sample purity from other methods (e.g. XRD, microscopic examination) indicates essentially no other contaminants.
b: The spectrum appears spectrally pure. However, other sample analyses indicate the presence of other minerals that probably affect the absolute reflectance level to a small degree, but do not add any spectral features. The spectral features of the primary minerals may be slightly less intense, but the feature positions and shapes should be representative. For example, in this wavelength region (W1), quartz would tend to increase the reflectance level and decrease absorption band strength, but would not add any measurable features to the spectrum. Such a sample would rate a "b." In a few cases, where we have little support data, but the spectra for that mineral are well known, we assigned the spectral purity based on the spectra data along with a microscopic examination of the sample. There are a few "b" classes done this way.
c: The spectrum is spectrally pure except for some weak features with depths of a few percent or less caused by other contaminants. For example, some minerals may have some slight alteration that is apparent. Spectroscopic detection of alteration is easier for more transparent minerals. For example, some of the albite spectra show weak 2.2-µm features due to alteration. From the knowledge of the mineral formula, you can often tell which features do not belong to the mineral. Albite, for instance does not have OH in the formula, so water features (1.4, 1.9, 2.2 µm) are not due to albite. However, you could argue that incipient alteration due to weathering is common in minerals at the Earth's surface. Thus, spectral bands due to weathering are somewhat characteristic of many samples (e.g. feldspars), even if they are not a property of the pure mineral. Thus these alteration spectral features might be useful in some cases.
d: Significant spectral contamination. The spectrum is included in the library only because it is the best sample of its type currently available and the primary spectral features can still be recognized. However, the spectrum should be used with care. The sample description should be consulted as a guide to what features are a part of the actual mineral. This sample may be purged from the database in future releases as better samples become available.
e: There are insufficient analyses and/or knowledge of the spectral properties of this material to evaluate its spectral purity. In general we have included such samples because we believe their spectra to be representative. These are samples for which we are concentrating future analyses in order to resolve the purity issue. Updates to the spectral purity and sample documentation will be placed online for anonymous ftp as the information becomes available. (See the section below on availability on how to electronically access the data and obtain further information.)

Commenting on the spectra in general, reflectance tends to decrease in the UV and beyond about 2.7 µm. Some of the spectra show minima in the UV. We have taken careful measurements of scattered light and believe all these features are real. Beyond 2.7 µm, even anhydrous minerals show absorption due to water adsorbed onto the surfaces of the mineral grains. Our experience has shown that these water absorptions are still present in dry nitrogen purged environments, although slightly weaker. Spectra of similar samples obtained at other facilities, like those in Hawaii or the east coast of the US. have shown us that the water absorptions in the spectra from relatively dry Colorado are really quite small in comparison. Placing the sample in a dry nitrogen atmosphere or a vacuum oven has little effect on the water absorption as water from the atmosphere will readsorb onto the sample by the time it reaches the spectrometer. Experiments by the senior author when he was at the University of Hawaii have also shown that most of the adsorbed water remains even under a strong vacuum at room temperatures. We decided in general not to heat our samples in order to avoid any temperature induced alteration.

The overall spectral purity is high for this library. Seventy-one percent of the spectra have a purity code of either a or b (36% a, and 35% b), while only 17% have c, and 2% have d. Ten percent are yet to be classified.


The wavelength precision of our custom-modified, computer-controlled Beckman spectrometer was checked using Holmium Oxide filters in the visible and the positions of known mineral bands in the near infrared. In particular, we developed pyrophyllite as a wavelength standard because of its many narrow absorption bands (Clark et al., 1990b). The positions of the absorption bands have been checked, using the same pyrophyllite standard, on two FTIR spectrometers. In general, the wavelength accuracy is on the order of 0.0005 *mm (0.5 nm) in the near-IR and 0.0002 *mm (0.2 nm) in the visible, always a small fraction of the spectral resolution.


Plots of the spectra presented here are limited to one of seven vertical scales (0.0 to 1.03, 0.8, 0.6, 0.5, 0.4, 0.3, or 0.2) and the same horizontal range for easy comparison. The error bars are plotted only when they are above a threshold that allows them to be distinguished on the plot. Most error bars are too small to be distinguished. At the bottom of each plot is the specpr title, date and time of acquisition, file name and record number and the specpr plot options.

Each spectrum was run with a desired signal-to-noise of at least 500 relative to unity reflectance. In practice, it would take too long a time to obtain such a signal-to-noise in regions where the signal is low, so an upper limit to the integration time per channel was also specified. Thus, typically at the ends of the spectra, the precision drops slightly. Refer to the error bars for each spectrum to determine the precision at a given wavelength for any individual spectral channel. The error bars are located in the records labeled "errors to previous data" and represent one standard deviation of the mean.

Each spectrum was measured relative to Halon, and then corrected to absolute reflectance as described in Clark et al. (1990b). That paper also describes the details of the spectrometer, and the viewing geometry of the system.


The intent of the spectral library is to serve as a knowledge base for spectral analysis. Comparison of spectral data is best done when the spectral resolutions of the knowledge base and the spectra undergoing analysis are identical. The specpr software has tools for convolving the spectral library to the resolution and sampling interval of any instrument. The native (laboratory) spectral library will also be convolved to AVIRIS and TM resolution and sampling for the terrestrial instruments, and to NIMS and VIMS for the planetary imaging spectrometer instruments. See Table 5 for a listing of instrument spectral libraries. These convolved data files, as well as specpr command files for convolving the database to your own instruments will be made available in the anonymous ftp directory (see below).

Each instrument convolved library requires about 0.8 megabyte of specpr-format disk space if the instrument has less than 256 channels. The proposed VIMS has 320 channels and its spectral library will be about 1.6 megabytes. The convolution to any other instrument (laboratory, or flight) is a simple matter of changing pointers in a command file to the custom resolution and sampling data sets and running the specpr command file. (Specpr runs on many Unix workstations; there is not a PC version at this time; a PC version might be difficult due to the large volume of code, over 60,000 lines.)

The convolution routine used to create the instrument spectral libraries is that in specpr. The specpr routine uses a trapezoidal integration over each bandpass. To make this integration more accurate, the original spectral library is resampled to 950 channels (splib04b) and the convolutions done on these spectra. The convolutions appear to be excellent, and tests with AVIRIS data have shown that very subtle spectral differences can be distinguished, like that between the 2.2-*mm doublet in kaolinite and halloysite.


This spectral library is largely a pure material library (except for a few cases where minerals tend to exist with other minerals). For computing intimate mineral mixtures (e.g. rocks or soils), radiative transfer algorithms using the Hapke reflectance model (Hapke, 1981) are part of the specpr package. To compute mixture or pure end-member spectra, a set of optical constants are required as a function of wavelength. The algorithms use the model at the optical constant level so spectra can be calculated as a function of grain size, abundance in the mixture, and viewing geometry. Reflectance spectra of grain size distributions can also be simulated by computing a mixture of the same mineral (or even several minerals) at several grain sizes. A future release of the library will include optical constants for the spectra in the library. Optical constant libraries will also be computed for the same flight instrument spectral resolutions and wavelengths shown in Table 5.

We included one mixture of hematite and quartz because we have found it useful in mapping hematite with imaging spectroscopy data. Usually, a pure hematite spectrum has bands that are too strong and saturated compared to that typically found in spectra of the Earth's surface. The mixture of hematite plus quartz simulates to some degree cases closer to those encountered in field data.


The software and spectral libraries are published as a series of USGS Open File Reports. The hardcopy spectral library, and users manuals are available from:

USGS/Dept. of the Interior
Books and Open-File Reports Section
U.S. Geological Survey
Box 25425, Federal Center
Denver, CO 80225

USGS Books, Open File Reports and Maps:
Phone number: (303) 236-7476

The relevant Open-File documents are:

93-592 Spectral Library paper version (this document), 1326 pages.

93-595 Specpr users manual, approximately 210 pages. (Clark, 1993)

93-594 Spsearch users manual, approximately 30 pages. (Gorelick and Clark, 1993)

93-593 Spview manual, approximately 15 pages. (Includes the digital spectral library and spectral library reader software on 3.5-inch floppy disks for IBM-PC compatible computers.) (Livo et al., 1993)

------------------------------------------------------------ ------------------------------------------------------------

NOTE: The instructions below are obsolete. Go to for the latest spectral library and instructions for downloading.

The digital data for the spectral library, software, and above manuals are available via anonymous ftp on the internet: 1. ftp 2. login as anonymous 3. password is your userid@machine 4. cd pub/spectral.library 5. get README

Follow instructions in the README file for obtaining the data. The pub/spectral.library directory will contain all the different versions listed in Table 5, as well as additional ones as they become available (again see the README file for details). Similarly, obtain the specpr and spsearch software in the pub/specpr and pub/spsearch directories. The specpr distribution also includes an independent Fortran program, spprint, that reads a specpr format file and prints titles. For independent subroutines in C that read a specpr file, see the README file.

After you have retrieved the library, please send mail to with your name, address, phone number and email address. We will put you on a mailing list for future announcements and updates.

Alternatively, contact any of the authors at their address, or send electronic (internet) mail if you have questions to :

A CD-ROM version will be available in the future.


A successful spectral library has extensive sample documentation. We are indebted to J. S. Huebner, and Judy Konnert of the USGS for their support in analyzing the X-ray diffraction data on minerals for the last couple of years. We thank the late Norma Vergo for many of the earlier X-ray analyses. Norma's attention to detail has certainly made this spectral library a quality product, and we miss her. Without these dedicated people providing superb analysis and feedback, this library would not have been possible.

Of course, a spectral library needs quality samples. We are indebted to Jim Crowley, Jim Post, Fred Kruse, and Jack Salisbury for donating excellent samples. Thanks to the British Museum and the National Museum of Natural History for mineral samples.

Several additional people worked on entering documentation for this database; a task that didn't seem to have an end. We thank Barry Middlebrook for completing some of the documentation on samples in the early stages, and Shelly Moore helped considerable entering data in the later stages of the project. Melissa Cowoski helped with the optical examination of the samples.

We thank Jim Crowley and Eric Livo for excellent reviews; they certainly helped improve the final version.

This project has been funded by the USGS DAT program, and the NASA HIRIS, Cassini VIMS, Mars Observer TES, and the canceled Mars Observer VIMS, and CRAF VIMS teams.


The senior author (RNC) is a team member on the EOS HIRIS flight investigation team and is developing spectral libraries for the team. He is also a team member on Mars Observer Thermal Emission spectrometer, and Cassini (mission to Saturn) VIMS teams. To satisfy the requirements of all these missions, the mineral spectral library will be extended to cover the spectral range 0.2 to 150 *mm and include many more minerals. For the HIRIS team, spectral libraries will be developed for all disciplines represented by team members.


Clark, R.N., 1980. A Large Scale Interactive One Dimensional Array Processing System, Pub. Astron. Soc. Pac., 92, 221-224.

Clark, R.N., T.V.V. King, and N.S. Gorelick, 1987. Automatic Continuum Analysis of Reflectance Spectra: Proceedings of the Third Airborne Imaging Spectrometer Data Analysis Workshop, JPL Publication 87-30, 138-142.

Clark, R.N., A.J. Gallagher, and G.A. Swayze: 1990a. Material Absorption Band Depth Mapping of Imaging Spectrometer Data Using a Complete Band Shape Least-Squares Fit with Library Reference Spectra, .I Proceedings of the Second Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) Workshop. JPL Publication 90-54, 176-186.

Clark, R.N., T.V.V. King, M. Klejwa, G. Swayze, and N. Vergo, 1990b. High Spectral Resolution Reflectance Spectroscopy of Minerals: J. Geophys Res. 95, 12653-12680.

Clark, R.N.: 1993. SPECtrum Processing Routines User's Manual Version 3 (program SPECPR): U.S. Geological Survey, Open File Report 93-595, 210 pages.

Fleischer, M.: 1980. Glossary of Mineral Species: Mineralogical Record, Tucson, 192pp.

Gorelick, N, and Clark, R.N.: 1993. Spsearch: a program for relational database queries of the digital spectral library: U.S. Geological Survey, Open File Report 93-594, (software complete, documentation in preparation).

Hapke, B., 1981. Bidirectional reflectance spectroscopy 1. Theory, J. Geophys. Res. 86, 3039-3054.

Klein, C. and Hurlbut, Jr., C.S. Manual of Mineralogy: John Wiley and Sons, 596pp, 1985.

Livo et al. 1993: PC Reader for the U.S. Geological Survey Digital Spectral Library: U.S. Geological Survey, Open File Report 93-593, .


Figure 1. The spectral resolution of the spectra in this release of the spectral library. The resolution is expressed as the Full Width at Half Maximum (FWHM) in micrometers. The spectral sampling is equal to the FHWM spacing. The sampling is one half Nyquist, such that if the response functions of the spectrometer were plotted for each wavelength, the half-maximum points would overlap the half-maximum points of the adjacent spectral channels. The FWHM rises where there is relatively low signal from the detector near the ends of the detector range. The spectral resolution is better than AVIRIS 1992 at all wavelengths except for a few channels near 0.87 µm and beyond 2.39 µm . The difference is so slight at 0.87 µm(12 nm versus 9 nm for AVIRIS) that for the spectral features encountered in this spectral library, there are no practical differences in AVIRIS convolved spectra. Beyond 2.39 µm, the Beckman rises to 22 nm at 2.42 µm and 32 nm at 2.50 µm compared to AVIRIS at a resolution of 14.6 nm in the 2.3 to 2.49-µm region. However, AVIRIS data are strongly affected by atmospheric absorption beyond 2.43 µm, so this difference is small in practice. Also, our future spectral library covering 2 to 150 µm will have resolution better than 2.5 nm in the 2 to 2.5-µm wavelength region.

The spectral resolution plotted here is our "standard 1x" resolution. Spectra are often obtained at higher resolution (1.5x, 2x, 3x, 4x, and 8x the standard). Some of these results have been reported in Clark et al. (1990b).


Individual description pages and plots of all apectra.

U.S. Geological Survey, a bureau of the U.S. Department of the Interior
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This page is maintained by: Richard Wise and Roger N. Clark
Previously modified August 23, 1999.
Last modified June 20, 2011 to point to updated spectral library and newer download instructions.