Waco Gem and Mineral Club, Waco, Tx

16.4 Collecting Preparing and Storing Miniature Fossils


16.4: Collecting, Preparing, and Storing Miniature Fossils

Collecting miniatures. Kids will find miniature fossils as they seek other, larger fossils during your regular field trips. In fact, a great many common invertebrate fossils fall within the size range of one- to two-inches and are often found weathered free at an outcrop: sea urchins and small sand dollars, small clams and snails, "Devil‘s toenail" oysters, a great many brachiopods, crinoid stem fragments, twiggy bryozoan, trilobites, horn corals, and more. You should also encourage kids to make trades with fellow collectors since they‘ll often bring home multiple examples of a fossil species. Encourage them to trade duplicate specimens from their collections with duplicates in other kids‘ collections to more quickly expand the variety of their holdings at no cost—while at the same time making friends within the hobby. Finally, they‘ll discover true bargains at gems shows for fossils that fall within the one- to two-inch size range, specimens that are a lot more affordable than big flashy fish fossils from Wyoming or two-foot limestone slabs with whole crinoids from Morocco.

Preparing miniatures. Preparing miniatures involves trimming away as much unnecessary matrix as possible without damaging the fossil. Basic supplies needed include hammers and small chisels (along with eye protection), rock nippers and pliers and/or special vice-like rock trimmers to snip away pieces of matrix, a small rock saw, and a regular hand magnifying glass or, better, a bench magnifier that allows you to work with both hands free. With a miniature fossil, you usually want to remove all the matrix, if possible, and Dremel-type bits and brushes and dental picks can help in removing final specks of dirt or matrix from small nooks and crannies. If the fossil has been silicified and is in a limestone matrix, soaking in vinegar (acetic acid)—followed by a vigorous brushing—can also help dissolve, loosen, and remove matrix. (Afterwards, soak the fossil in water and baking soda to neutralize any remaining acid from the vinegar.)

If a specimen is delicate or can really only be exhibited in matrix, as much matrix as practical should be removed. If a specimen is in hard limestone or shale, a small rock saw or a hack saw fitted with a grit-edge or tungsten carbide blade rod is often used. However, many collectors prefer a "natural" edge to the matrix rather than the flat edge that a saw produces. One way to create a natural edge is to saw a groove from below and then tap with a small chisel and lapidary hammer from above. When hammers and chisels are being used to remove matrix that‘s very close to a specimen, the rock should be placed on a sand bag to cushion blows.

Storing miniatures. Miniatures may be stored in egg cartons, small fold-up cardboard boxes, or in 2-inch Perky boxes, named after their creator, Willard Perkins. These small plastic boxes, available from mineral suppliers, usually have a black bottom lined with Styrofoam and a clear plastic top. These Perky boxes, in turn, can be stored in soda flats or small cabinets.

Note: Kids can use this activity to satisfy requirements toward earning the Collecting badge simultaneously (Activity 5.1).