Amber, a fossilized tree resin, is prized both for its beauty and the biological inclusions it sometimes holds. Formed over millions of years as resin undergoes polymerization, this organic gemstone is a sought-after material for collectors and scientists alike. Locating this prehistoric material in the United States requires knowledge of specific geological contexts. This article explores where documented deposits exist across the nation and provides practical methods for identifying a genuine find.
Documented Amber Deposits in the USA
The United States hosts amber deposits, though they are often smaller and more fragile than the Baltic material. One significant find is Cretaceous-age amber, found in the Raritan and Magothy Formations of the Atlantic Coastal Plain. This material, approximately 90 to 94 million years old, is distributed across New Jersey, Maryland, Staten Island, Long Island, and Martha’s Vineyard in Massachusetts. While typically small and brittle, this amber is highly valued for its paleontological content, yielding diverse ancient inclusions, including the oldest known ant and bee species.
Another notable US deposit is located near Malvern, Arkansas, where the largest concentration of specimens in North America has been discovered. This Eocene-age amber, found within lignite beds of the Claiborne Formation, contains preserved insects, plants, and arachnids. Further north, Tertiary-age amber is documented in Alaska, particularly in the Eagle-Circle district south of the Yukon River, often associated with coal seams.
These US deposits are generally not sources of the large, gem-quality nuggets used in commercial jewelry, but they hold immense scientific value. Small, isolated finds have also been reported in states such as California, Montana, and New Mexico, including detrital amber pebbles found in the Upper Triassic Chinle Formation in Arizona.
Techniques for Identifying Real Amber
Distinguishing true amber from common simulants like copal (younger resin), glass, or plastic requires simple, non-destructive tests based on its unique physical properties.
Saltwater Float Test
One accessible method is the saltwater float test, which takes advantage of amber’s low density. A saturated solution made by dissolving seven to eight teaspoons of salt in a glass of water will cause genuine amber to float, while most denser fakes, including glass and plastic, will sink.
Static Charge Test
Another reliable method is the static charge test. When true amber is rubbed vigorously with a piece of natural fabric, it quickly builds up a negative electrostatic charge. This charge can be tested by holding the specimen near small paper pieces or a strand of hair, which will be visibly attracted. If the material becomes sticky instead of attracting paper, it is likely copal, a younger and less-hardened resin.
Smell Test
A final identification technique involves a careful smell test. Heating a needle and touching it to an inconspicuous spot on the specimen will cause genuine fossilized resin to emit a characteristic, pleasant, resinous, or pine-like odor, distinct from the chemical smell of heated plastic. Amber will resist the needle more than plastic, and the needle will only slightly penetrate the surface.
Guidelines for Collecting on Public Land
Collecting amber on public lands is governed by strict regulations that vary significantly by agency and location. Searching for any mineral resource in National Park Service (NPS) units is prohibited by federal law. This ban applies to National Parks, National Monuments, and most other areas managed by the NPS.
Conversely, lands managed by the Bureau of Land Management (BLM) are often open for recreational rockhounding. The BLM typically allows the casual, noncommercial surface collection of reasonable amounts of rocks and minerals without a permit. This collection must not involve extensive excavation or motorized equipment.
National Forests also permit limited collection for personal, noncommercial use, often restricting the amount to around 10 pounds. Regardless of the public land jurisdiction, collectors must always confirm local rules with the specific field office, and any collection on private land requires explicit permission from the landowner. Adhering to the principle of non-destructive searching is paramount.