Tools and directories

The words, in the order you meet them

Updated October 2026

On this page5

The specimen The sizes The failures The rules References

Terms as you meet them rather than alphabetically.

The specimen

Species. Defined by chemistry and crystal structure, formally approved. The only name that is a factual claim about what the material is.

Variety. A recognizable form of a species, with no formal standing. Amethyst is a variety of quartz.

Habit. The characteristic shape a crystal takes.

Matrix. The host rock the crystal grew on. Part of the specimen, not packaging.

Termination. Whether a crystal ends in natural faces or a break. Doubly terminated means complete at both ends.

Contact. A surface where the crystal grew against something. Natural, and not damage.

Float. Material found loose, away from its source.

The sizes

Micromount. Viewed under magnification, mounted in a box.

Thumbnail. Fitting within a one-inch cube in any orientation.

Miniature, small cabinet, cabinet: the display classes, in ascending size.

Flat. A shallow subdivided tray, and the trading unit of the hobby.

Perky box. The clear-lidded cushioned box thumbnails live in.

The failures

Pyrite decay. Sulfide oxidation above about 60% relative humidity, producing iron sulfates and sulfuric acid. The acid destroys the label and the box too.

Byne's disease. Acid vapor reacting with calcium carbonate to form calcium acetate and formate efflorescence. Named from shell collections, and the acid usually comes from the storage.

Dehydration. Hydrated species losing structural water and going chalky. Laumontite is the classic.

Fugitive color. A color that fades in light. Realgar, amethyst, rose quartz.

The rules

The BLM allowance. 25 pounds per day plus one piece, 250 pounds a year, noncommercial.

Noncommercial. The word the allowance turns on. Selling requires a permit or a claim.

36 CFR 2.1. The National Park Service prohibition on removing specimens.

PRPA. The Paleontological Resources Preservation Act. Vertebrate fossils on federal land remain federal property.

As received. The honest qualifier for a locality you did not verify.

References

US Bureau of Land Management. Public Collection of Rocks, Mineral Specimens and Semiprecious Gemstones: FAQs (2024). Sets the reasonable personal-use amount at 25 pounds per day plus one piece, and not more than 250 pounds in a year, and excludes developed recreation sites, areas under active claim and land where the mineral estate is privately owned. blm.gov

Canadian Museum of Nature. Pyrite disease. Pyrite oxidizes in the presence of oxygen at elevated relative humidity, expanding into iron sulfates and producing sulfuric acid that attacks labels and storage materials alongside the specimen. nature.ca

US National Park Service. Conserve O Gram 11/15, Byne's "Disease". Acid vapor reacting with calcium carbonate to form calcium acetate and formate efflorescence, accelerated by high relative humidity. nps.gov

US National Park Service, 36 CFR 2.1, which prohibits possessing, destroying or removing from a park any mineral, rock or paleontological specimen except as specifically authorized. ecfr.gov

Paleontological Resources Preservation Act of 2009, 16 U.S.C. 470aaa. Vertebrate fossils on federal land require a permit and remain federal property; common invertebrate and plant fossils may be collected in reasonable amounts for personal, noncommercial use. blm.gov

Written from the federal land-management rules, the conservation literature and the agency guidance named on each page. Collecting rules differ by agency, by unit and sometimes by parcel, and the land manager for the ground you are standing on is the authority on it, not this page.