Starting a Rock Collection

Source: US Geological Survey

A good rock collection consists of selected, representative specimens, properly labeled and attractively housed. It 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 one's home. These stones may have little value in the collection 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 one becomes more familiar with collecting methods and with geology, the collection will probably take one of two directions. One may try either to obtain representative specimens of igneous, sedimentary, and metamorphic rocks, or to collect all the related kinds of rocks from particular geologic provinces.

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, unsurpassed as collecting guides, 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 book reports. Most geologic maps are issued by public or private scientific agencies. The most prolific publisher in the United States is the U.S. Geological Survey. "Geologic and Water-Supply Reports and Maps, (State)," a series of book lets, provides a ready reference to these publications on a State basis. The booklets also list libraries in the subject State where Geological Survey reports and maps may be consulted. These booklets are available free on request and may be obtained from: Book and Open-File Reports Section U.S. Geological Survey Federal Center, Box 25425 Denver, CO 80225 Residents of Alaska may write to: U.S. Geological Survey 108 Skyline Building 508 Second Avenue Anchorage, AK 99501 Geologic organizations of many States also publish geologic maps, as do many universities and scientific journals. Geologic maps can be located through public, research, 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. Smaller rock collections abound in libraries, schools, public buildings, small museums, and private homes.

Where To Find Rocks

Collections usually differ markedly depending on where the collector is able to search for rocks. In the great interior plains and lowlands of the United States, the sedimentary rocks are exposed in wide variety. Igneous and metamorphic rocks are widespread in the mountains and piedmont areas of New England, the Appalachians, the Western Cordillera, and scattered interior hill lands; igneous rocks make up almost all the land of Hawaii. Along the Atlantic and Gulf Coastal Plains and locally elsewhere, loose and unconsolidated rocks are wide spread; in northern areas glaciers deposited many other unconsolidated rocks.

The best collecting sites are quarries, road cuts or natural cliffs, and outcrops. Open fields and level country are poor places to find rock exposures. Hills and steep slopes are better sites. Almost any exposure of rock provides some collection opportunities, but fresh, unweathered outcrops or manmade excavations offer the best locations. Where feasible, it is a good plan to visit several exposures of the same rock to be sure a representative sample is selected.

Collecting Equipment

The beginning collector needs two pieces of somewhat specialized equipment- a geologist's hammer and a hand lens.

The hammer is used to dislodge fresh rock specimens and to trim them to display size. It can be purchased through hardware stores or scientific supply houses. The head of a geologist's hammer has one blunt hammering end. The other end of the most versatile and widely used style is a pick. This kind of hammer is aptly called a geologist's pick. Another popular style-the chisel type-has one chisel end; it is used mostly in bedded, soft sedimentary rocks and in collecting fossils.

The hand lens, sometimes called a pocket magnifier, is used to identify mineral grains. Hand lenses can be purchased in jewelry stores, optical shops, or scientific supply houses. Six-power to ten-power magnification is best. Optically uncorrected hand lenses are inexpensive and quite satisfactory, but the advanced collector will want an optically corrected lens.

Other pieces of necessary equipment are neither unusual nor expensive: a knapsack to carry specimens, equipment, and food; paper sacks and wrapping paper in which to wrap individual specimens; a notebook for keeping field notes until more permanent records can be made; and a pocket knife, helpful in many ways, especially to test the hardness of mineral grains.

On some collecting trips, additional equipment is desirable. Sledge hammers can be used to break especially durable ledges. Cold chisels often make it possible to loosen specimens. Dilute hydrochloric acid assists in identifying limestone and dolomite. A long list could be made of such equipment; the collector must decide for each expedition which tools are really worth the weight.

Housing and Enlarging a Collection

The practical problems of cataloging and storing a collection are ones that every collector must consider. If desired, housing arrangements can be very simple because rocks are durable and do not require special treatment. Cigar boxes and corrugated cardboard boxes are often used. Ordinary egg cartons can be used if the specimens are rather small. Shallow wall cases for rock collections are available commercially.

It is important to have a careful system of permanent labeling so that specimens do not get mixed. Many people paint a small oblong of white lacquer on a corner of each specimen and paint a black number on the white oblong. A notebook is used to enter the number, rock name, collector's name, date collected, description of collection site, geologic formation, geologic age, and other pertinent data. If rocks are kept on separate trays, a small card containing some data is usually placed in the tray.

Extra specimens are sometimes used for trading with other collectors. Few people have the opportunity to obtain all varieties of rock types, and exchanging can fill gaps in a collection. Collectors interested in trading are usually located by word of mouth. No countrywide organization of rock collectors exists, though local clubs and individual collectors are numerous throughout the United States. It may be necessary to buy some specimens, but this should be done selectively because good specimens are expensive.

Hints for Rock Collectors

1. Label specimens as they are collected. Identification can wait until later, but the place where the rocks were found should be recorded at once. Many collections have become confused because the collector did not do this.
2. Trim rocks in the collection to a common size. Specimens about 3 by 4 by 2 inches are large enough to show rock features well. Other display sizes are 2 by 3 by 1 inch, or 3 by 3 by 2 inches.
3. Ask for permission to collect rocks on private property. The owners will appreciate this courtesy on your part.
4. Be careful when collecting rocks. Work with another person, if possible, and carry a first aid kit. Wear protective clothing-safety glasses, hard-toed shoes, hard hat, and gloves-when dislodging specimens. Avoid overhanging rock and the edges of steep, natural or quarried walls.
5. Do not collect rocks in national parks and monuments or in State parks, where it is illegal to do so. Similar rocks commonly crop out on land nearby, and can be collected there.
6. Look for unusual rocks in large buildings or in cemeteries. Dimension stone blocks and monument stone are often transported long distances from where they are quarried. Polished stone sometimes looks different from unpolished rock. This provides good identification practice.
7. Join a mineral club or subscribe to a mineral magazine. They occasionally discuss rocks.
8. Collecting rocks from each State or country has no scientific significance. The distribution of rocks, a natural phenomenon, is not related to political divisions.