Waco Gem and Mineral Club, Waco, Tx

16.2 Collecting Preparing and Storing Thumbnail Minerals


16.2: Collecting, Preparing, and Storing Thumbnail Minerals

Collecting thumbnail minerals. See 16.1 on ways to collect miniatures. It‘ll be much the same when approaching thumbnails. However, the 'tools of the trade' get a little more specialized. You‘ll need the same tools used for collecting miniatures, augmented with a loupe, flat screwdrivers and ice picks, and chisels of various sizes but especially small ones. The screwdrivers and ice picks can be used to probe small crystal-lined pockets and to remove mud and clay from cavities. If trying to chip out a little crystal-lined vug, stuff bits of rags (or shaving cream) into the cavity, both to protect crystals from shocks of hammer blows and to keep them in place so they don‘t go flying. In areas where small crystals may be loose in the dirt or gravel or when searching through mine tailings, your best tools are hand rakes, small shovels or trowels, and quarter-inch mesh screens in wooden frames. This is how many fee dig sites operate, with a pile of earth from mine tailings to be dumped into screens and sifted in water for quartz crystals, tourmalines, garnets, etc. Also handy: a supply of small zip-lock baggies to store finds.

Preparing thumbnail minerals. For thumbnails, as with miniatures, the goal is to reduce larger rock blocks with hammers and chisels if the crystals can take the shock of blows being delivered around them. You want to trim away as much matrix as possible without damaging the crystals, switching to increasingly delicate techniques the closer you get. Instead of delivering sharp blows with a standard rock hammer and chisel, you‘ll switch to small chisels and deliver delicate blows with small lapidary hammers (while wearing eye protection). You can also use rock or tile nippers and vice-like rock trimmers. For especially stubborn matrix, you may need to use a trim saw lubricated with water rather than oil, but most collectors prefer a 'natural' edge on matrix as opposed to the straight edge of a saw cut. One way to create a natural edge is to saw a shallow groove from below and then tap with a small chisel and hammer from above. When using hammers and chisels to remove matrix close to your specimen, place your rock on a sand bag to cushion blows, and use a bench magnifier to leave both hands free. Two other important tools are tweezers and glue should a crystal in a cluster pop loose.

Storing thumbnail minerals. Thumbnails are best stored in 1-inch Perky boxes, which are actually 1.25"x1.25"x1.25". These small acrylic boxes, available from mineral suppliers, have a black bottom lined with Styrofoam and a clear top. Specimens can be glued onto or pushed into the Styrofoam or attached with tack. Instead of Styrofoam, you can also use 1-inch acrylic squares that make it easy to remove a specimen from the Perky box for display in an exhibit. For kids just beginning and on a budget, matchboxes will also do, or—as with miniatures—plastic boxes with compartments and fold-top lids sold in bead stores or with fishing tackle. The bottom of each compartment should be lined with cotton to keep specimens from rolling about. Basically, use anything that‘s enclosed so as to contain the small specimen securely and to keep out dust.

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