- Adapted from COLLECTING ROCKS by Rachel M. Barker
Starting a Collection
A good rock collection consists of selected, representative, properly labeled specimens. The collection can be as large or as small as its owner wishes. An active collection constantly improves as specimens are added or as poor specimens are replaced by better ones. A rock collection might begin with stones picked up from the ground near your home. These stones may have limited variety and can be replaced later by better specimens. Nevertheless, this first step is helpful in training the eye to see diagnostic features of rocks (features by which rocks can be differentiated). As you become more familiar with collecting methods and with geology, the collection will probably take one of two directions. You may try either to collect as many different types of igneous, sedimentary, and metamorphic rocks as possible, or to collect all the related kinds of rocks from your own particular area.
Identifying Rocks
Many books about geology explain the identification and classification of rocks and describe the underlying geologic principles. Almost any recent general book on geology would help a rock collector. Geologic maps, which are useful guides for collecting, are also excellent identification aids. They show the distribution and extent of particular rock types or groups of rock types. Depending on size and scale, the maps may cover large or small areas. Most have brief descriptions of the rock types. Some are issued as separate publications; others are included in books.
Most geologic maps are issued by public or private scientific agencies. The most prolific publisher of geologic maps in the United States is the U.S. Geological Survey (USGS). "Geologic and Water-Supply Reports and Maps, (State)," a series of booklets published by the USGS, provides a ready reference to these publications for 13 States. The booklets also list libraries in the subject State where USGS reports and maps may be consulted. These booklets are available for less than $5.00 and may be obtained from:
USGS Information Services
Box 25286
Denver, Co 80225
Residents of Alaska may write to:
U.S. Geological Survey
Room 101
4230 University Drive
Anchorage, AK 99508-4664
Older catalogs are available free of charge at the locations listed above. Geologic organizations of many States also publish geologic maps, as do many universities and scientific journals. Geologic maps may be located in public or university libraries.
Comparing one's own specimens with those in a museum collection can help in identifying them. Most large rock collections are well labeled. Small rock collections abound in libraries, schools, public buildings, small museums, and private homes.
