What size box does each specimen need?

Size the box by the specimen's largest dimension. A thumbnail, a piece about an inch across, goes in a 1.25 inch box, usually the small plastic cube collectors call a perky box; a miniature, about 2 inches, goes in a 2.5 inch cube [1]. Above miniature there is no published standard box, so you measure, add room for padding and the label, and choose the nearest size you can buy in quantity. This page gives the class limits and box sizes in one table, shows how to measure, and explains why keeping one box size per drawer saves space.

Size classes and the box that goes with each

Size classes are the collector's way of grouping specimens by their largest dimension. No standards body sets them: the published limits are dealer definitions, and they differ by a quarter inch or more. The full comparison, including the Denver show's competition sizes, and which to follow for cataloging and for competition, is on size classes. The table below uses two dealers' definitions, McDougall Minerals and iRocks, because they are the ones that pair classes with boxes, and adds the box sizes they give.

Two points about the table.

The thumbnail limit depends on who is counting. McDougall Minerals, a dealer, defines a thumbnail by the 1.25 inch box, and notes that the current American Federation of Mineralogical Societies (AFMS) definition is "only 2.5cm/1″" [2]. If you enter competitions, the show's own rules decide. For storage, the 1.25 inch box is what matters, and a specimen that fits one sits in a thumbnail drawer whatever you call it.

The box is larger than the class limit. iRocks pairs a 2 inch miniature with a 2.5 inch cube [1], which leaves a quarter inch on each side for padding and for seating the piece on its best face.

How to measure a specimen for a box

1. Measure in three directions. A Mindat article written for people sorting collections says to "measure in 3 directions and to measure in Centimetres!" [4]. Record length, width and height in that order, largest first.
2. Use the largest of the three to choose the size class and the box.
3. Add room for the seat. If the piece sits on a foam pad or pedestal, measure its height with that support in place. A thumbnail that fits a 1.25 inch box loose may not fit once it is raised on a mount.
4. Leave room for the label. In small boxes the label usually goes under the base or folded beside the piece; in larger boxes it should be readable without lifting the specimen. Label placement is covered on keeping labels with specimens.
5. Check the lid. Crystal points must clear the lid with space to spare. A box that touches a termination will eventually chip it.
6. Write the dimensions in the catalog. You will use them again when you list, sell or ship the piece.

When a specimen falls between sizes

The awkward pieces are the toenails and the flat or long specimens.

• A specimen just over a thumbnail: go up to the miniature box and pad it, rather than forcing a fit. Forcing is how points break.
• A long, thin specimen: size by length. A 3 inch blade in a box made for its width will rattle or snap.
• A plate: size by the plate's footprint, and check the height of the tallest crystal.
• A heavy specimen: a light plastic box may crack under the weight when lifted by the lid. Use a sturdier box or an open tray in a drawer, and lift the piece, not the box.

Cushioning materials, and which ones last in a closed box, are on cushioning.

One size per drawer saves the most space

Mixed box sizes waste drawer space because the gaps between unequal boxes cannot be filled. A drawer of a single box size packs edge to edge. The arithmetic is simple: a drawer with an inside floor of 20 by 15 inches holds a grid of 16 by 12, or 192, boxes of 1.25 inches, and 8 by 6, or 48, boxes of 2.5 inches. Measure your own drawer's inside dimensions before you buy boxes, since a drawer that is a quarter inch short of a multiple loses a full row.

Space is one reason collectors give for specializing in small sizes. iRocks puts it this way: "approximately 500 thumbnails could fit into the same display space as 25 hand-sized specimens" [1]. Some serious collectors also keep their thumbnails as a separate collection; the collector John Barlow "separated out his thumbnails into a separate display collection with separate numbering" [3].

The same thinking appears in older sources. A 1957 Arizona Highways article on small specimens noted that with the partitions removed, "sixty-six paper boxes" of the micromount size would fit in one standard thumbnail competition box [5]. Boxes have changed; the logic of matching the drawer to the box has not.

Keep drawers from shifting as well. The National Park Service suggests that "Magnets or empty trays used as space holders in a drawer will prevent specimen trays from shifting within drawers" [6]. A half-empty drawer of loose boxes is a drawer of boxes sliding into each other every time it opens.

Box material matters as much as box size

A correctly sized box in an unstable plastic can still harm a specimen over years. The Canadian Conservation Institute names PET among "the most commonly used materials for small clear plastic boxes" [7], and conservation sources rate the common box plastics differently. Which resins they consider stable, and what to ask a supplier, are on which plastic is safe for specimens.

From the box to the drawer and the cabinet

Once the box sizes are settled, the next decision is how the drawers are arranged so you can find any piece again. That is covered on flats, drawers and cabinets. If most of your collection is thumbnails, the perky box itself, its parts and how to mount a piece in one, is on perky boxes and thumbnails.

References

1. iRocks, *Size Matters! Collecting Miniature Mineral Specimens*, June 9, 2016. https://www.irocks.com/size-matters-collecting-miniature-mineral-specimens
2. Raymond McDougall, McDougall Minerals, *Size Matters!*, page dated 12.09.2013. https://mcdougallminerals.com/?p=33
3. Jim Houran, Jim Bleess and Alex Schauss, *Little Wonders: Connoisseur Thumbnails in the Contemporary Collector Market*, iRocks, April 7, 2020. https://www.irocks.com/little-wonders-connoisseur-thumbnails-in-the-contemporary-collector-market
4. Bri Dragonne, *Advice for people selling and sorting a mineral collection*, Mindat.org article 836, last updated November 19, 2009. https://www.mindat.org/article.php/836/Advice+for+people+selling+and+sorting+a+mineral+collection.
5. A. L. Flagg, *Petite Minerals*, Arizona Highways, November 1957. https://www.arizonahighways.com/archive/issues/chapter/Doc.406.Chapter.2
6. National Park Service, Kathy Hall, *Storage Concerns for Geological Collections*, Conserve O Gram 11/2, April 1998. https://www.nps.gov/subjects/museums/upload/11-02_508.pdf
7. Canadian Conservation Institute, Jean Tétreault, *Products Used in Preventive Conservation*, Technical Bulletin 32, issued February 7, 2018, modified February 19, 2021. https://www.canada.ca/en/conservation-institute/services/conservation-preservation-publications/technical-bulletins/products-used-preventive-conservation.html