How to display specimens without harming them
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A safe display case keeps light, heat, dust, acid vapors and hands away from the specimens inside it. In practice that means a case of glass or cell cast acrylic [1], case materials that do not give off acids [2][3], lights that do not heat the case and are filtered for ultraviolet [4], light-sensitive species kept out of the display entirely [4], and every piece secured against knocks and earthquakes. This page takes those risks one at a time, compares sealed and vented cases, and covers labels and security. The light levels themselves live on light fading.
Decide what goes in the case before you choose the case
The first protection is selection. The National Park Service says "Light sensitive mineral specimens should not be exhibited and should be stored in closed cabinets" [4]. Before you build or buy a case, sort the pieces you want to show:
| Group | Examples of the concern | Display decision |
|---|---|---|
| Light-sensitive species | Species known to fade or alter in light; see light fading | Keep in closed storage; show a photograph instead, or display briefly in low light |
| Humidity-sensitive species | Pyrite and marcasite (decay above 60 percent RH), deliquescent and hydrated minerals [4] | Only in a case whose humidity you can monitor and hold |
| Acid-sensitive species | Calcite and other carbonates, shells | Only in a case built from tested, low-emission materials [2][3] |
| Hazardous species | Toxic, asbestiform or radioactive specimens | Not in a home display; see dangerous minerals |
| Stable species | Most quartz, agate, garnet, many silicates | The best candidates for long display |
Case materials
| Material | Use | What sources say |
|---|---|---|
| Glass | Doors, shelves, panels | Inert; heavy and breakable. The earthquake that "shattered the glass cases and shelves" of one well-known thumbnail collection is a reminder to secure it [5] |
| Cell cast acrylic | Case tops, covers, panels | CCI: "recommended for framing and display cases because of its superior optical clarity" [1]. CCAHA describes acrylic glazing as "scratch-resistant and low static, as well as UV filtering" [3] |
| Polycarbonate | Glazing where breakage or theft is a worry | CCI: "polycarbonate resists shattering, which gives it a security advantage," but it "is not as easy to glue due to its resistance to solvents" [1] |
| Powder-coated or baked enamel steel | Frames and bases | NPS favors metal storage furniture [2]; CCAHA says baked enamel is acceptable only if tested for proper baking with a solvent rub test [3] |
| Wood, board, paints, adhesives, sealants | Bases, backs, decorative cases | NPS: wood, coatings, adhesives and sealants can release acids, and in a sealed case "these gases cannot escape" [2]. CCAHA: "Safe tested materials (Oddy test) must be used for mounts, such as coatings and paints" [3]. What the Oddy test is: which plastic is safe |
| Fabric linings | Case floors and backs | CCAHA: unsized, unbleached, undyed cotton, washed first, can be used "in exhibition cases" [3] |
If you build a wooden case or paint one, let it cure before specimens go in. CCI advises that adhesives in enclosures "should be allowed to off-gas or dry out (cure or set) for three to four weeks" [1], and warns that acetoxy-cure silicone sealant, the common household kind, releases acetic acid [1].
Sealed or vented
A sealed case keeps out dust and pests and slows humidity swings. A vented case lets vapors escape. Which is right depends on the case's materials and on what is inside.
| Sealed case | Vented or loose-fitting case | |
|---|---|---|
| Dust and pests | Kept out | Gets in slowly; needs cleaning |
| Humidity | Changes slowly; can be held with conditioned silica gel | Follows the room |
| Vapors from case materials | Trapped and concentrated [1][2] | Diluted by room air |
| Best for | Cases built from metal, glass and tested materials; humidity-sensitive species | Cases with wood or uncertain materials holding stable species |
| What to watch | Gaskets age: CCI says a polyurethane gasket has "a limited lifespan" of about 10 to 20 years [1]; airtight cases "Must use sealed seams and adequate gaskets" [1] | Dust on fragile crystals; light and heat from the room |
CCI sums up the trade-off: tight enclosures "are an excellent preventive conservation strategy on many fronts," and "the most dangerous scenario is when a vulnerable object is placed in a well-sealed enclosure" with a large area of emissive material [1]. Seal the case only if you trust what it is made of. Holding a set humidity inside a closed container is covered on sealed storage.
Light and heat from the lights
Light causes fading in sensitive species, and the lights themselves can heat a case.
Ultraviolet. NPS: "UV filters on light fixtures will block out ultraviolet light" [4]. Acrylic glazing that filters UV adds a second barrier [3]. Specific light and UV levels for display, with their source, are on light fading.
Time. NPS's advice for storage applies to displays too: "Keep lights off when people are not in storage" [4]. A timer or a switch at the case does more than any filter.
Heat. A museum manual on geological collections lists "fracturing or volatilisation of crystals by exposure to heat or cycles of hot and cold" among the risks to mineral specimens [6]. Lights mounted inside a closed case, sunlight through a window, and a case on a radiator or against an outside wall all create those cycles. Mount lights outside the case where you can, keep the case out of direct sun, and feel the glass and the shelf after the lights have been on for an hour: if they are warm, the specimens are too. Thermal shock and the species most prone to it are on heat and thermal shock.
Mounting specimens in a case
A display mount has one job: hold the specimen still at its best angle without marking it. NatSCA's guidance for displayed geological specimens asks for mounts that are secure and stable, with padding that will not damage the piece [7].
- Seat each piece on a cradle, a stand shaped to its base or a pad of plain polyethylene foam; see cushioning.
- Avoid adhesive or tape on the specimen itself; CCI calls this "unsafe and not recommended" [1].
- Keep tall or top-heavy pieces low and toward the back.
- In earthquake country, secure the case to the wall and give each piece a lip, a cradle or a discreet restraint.
Labels in a display
A display label and the data label are two different things.
- The display label is for visitors: species, locality, perhaps a line on why the piece matters. It can be printed fresh and changed.
- The data label is the specimen's record and stays with it. NatSCA's rule is to keep every label with its specimen or box [7]. Put the original label under the base, in an envelope behind the piece, or in the specimen's storage box with a card saying where the specimen is now.
- Record in the catalog that the piece is on display and where, so it can be found; see flats, drawers and cabinets.
Label paper and ink that last are covered on what to print a label on.
Security
- Lock the case. NPS says cabinet doors "should seal tightly and have locks" [4]; the same applies to a display at home or in a shop.
- Use shatter-resistant glazing where theft is a risk; polycarbonate resists breaking [1].
- Do not display the most valuable pieces near a window that can be seen from outside.
- Photograph the display and keep the catalog current, so a loss can be documented.
- Check your insurance. Collections on display may be subject to sublimits and exclusions; see insurance, and what your policy excludes.
Keeping the case in good order
Clean the glass with the specimens removed, dust only robust specimens (NPS says "Friable specimens should never be dusted" [4]), look for fading, efflorescence or powder at each annual check, and rotate sensitive pieces back into dark storage. The yearly checklist is on the annual condition check. For the full picture of light damage, including which species fade and the light levels museums use, go next to light fading.
References
- 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
- National Park Service, Greg McDonald, *Health and Safety Issues with Geological Specimens*, Conserve O Gram 11/11, September 2006. https://www.nps.gov/subjects/museums/upload/11-11_508.pdf
- Conservation Center for Art and Historic Artifacts (CCAHA), *Selecting Materials for Storage and Display*, undated. https://sustainableheritagenetwork.org/system/files/atoms/file/Selecting%20Materials%20for%20Storage%20and%20Display_CCAHA.pdf
- 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
- 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
- Western Australian Museum, *Geological Collections*, online museum manual (manual.museum.wa.gov.au), undated, read October 22, 2026. https://manual.museum.wa.gov.au/book/export/html/52/index.html
- Emma Nicholls, Horniman Museum and Gardens, *Care and Use of Geological Collections*, Natural Sciences Collections Association (NatSCA), undated. https://www.natsca.org/sites/default/files/Care%20and%20Use%20of%20Geological%20Collections-%20NatSCA.pdf
