Reference Sources give you quick facts, well-digested summaries of concepts, tables of properties, etc. 

Basically, if you want a quick fact or an overview of something, you might just find it faster in a reference book.

Types of Reference Books:

NOTE:  Most examples are in the reference collection, or `ask at desk´--check the library catalog and/or the circulation desk for details.   

   Scientific Encyclopedias:  Remember how useful the World Book Encyclopedia was, or the Encyclopedia Brittanica?  Scientists have their own encyclopedias--which contain more technical synopses of EAS terms, famous places, properties, etc.  
         Examples:  Encyclopedia of Minerals, 549.03 R544e 1990
        See also: AccessScience.com -- an online version of the McGraw-Hill Encyclopedia of Science and Technology.  It isn´t as specialized as an EAS encyclopedia, but does contain most basic concepts from the earth sciences. 

    Scientific Dictionaries:  If you just want a short definition of a technical term, use a dictionary.  The definitions will be much more precise than those found in a regular dictionary.
       Examples: Glossary of Geology, 550.3 Am3g 1997
        See also:  AccessScience.com -- includes a scientific dictionary on its site.

    Field Guides:  Collections of information on a topic that might come in handy when doing field work.  Contains, for example, simple properties of objects, perhaps locations where they may be found
       Examples:  National Audubon Society field guide to North American rocks and minerals / Charles W. Chesterman ; scientific consultant, Kurt E. Lowe.  552.097 C426a 1995
        Simon and Schuster's Guide to rocks and minerals / edited by Martin Prinz, George Harlow, and Joseph Peters  552.075 M858mE
      

     Handbooks/Tables:  Compilations of data into tables, charts, and graphs, so you only have to look in one place to find the properties of your material. 
       Examples: Handbook of Mineralogy, 549 H191 1990
                         Dana´s New Mineralogy,   549 D19s 1997
                         Rocks and minerals : all-color guide 552 Ar32r 1991

     Atlases and Maps:  Compilation of data in a geospatial format.  For example, giving locations of bedrock layers, earthquakes, minerals, etc.
      Examples: Atlas of Economic Mineral Deposits,
553 D643a

Indexes and Bibliographies: Provides a list of resources related to a particular subject.
Examples: Hey's Mineral Index, 549 B77i 1993