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How to Catalog a Mineral Collection So Nothing Gets Lost

By Digital Towns Crystals ยท Last reviewed October 8, 2026

Short answer: give every specimen one permanent number, put that number on the specimen itself, and write it on a label and in a catalog record that holds the species, locality, size, source, date and price. Print labels on acid-free paper with pigment or carbon ink, photograph each piece with its number visible, and keep the catalog in three copies, one stored away from the house. The number is the thread that ties rock, label and record together.

Why does a collection need a catalog at all?

A specimen carries some information in itself: species, color, habit, weight. The one thing it cannot carry is where it came from. The Mineralogical Society of America's collecting advice makes the point bluntly: locality is usually the only thing you can't tell later about a specimen, and a missing locality will often completely destroy its scientific value and its commercial value too.

A label alone does not solve that. Labels slide out of boxes, get swapped when two pieces are cleaned on the same towel, and fade. A catalog adds a second, independent copy of the information, and a number on the specimen links the two. If the label is lost, the number on the rock still finds the record. If the record file is lost, the label and the number still match.

The scale museums work at shows why they never rely on memory. The Natural History Museum in London says its mineralogy collections comprise around 500,000 rocks, gems and minerals, including about 5,000 meteorites, and that the collections are being digitised and made searchable through the museum's Data Portal. A home collection of 200 pieces runs on the same principle, just with a spreadsheet instead of a registry department.

How should you number specimens?

Pick one scheme and never reuse a number, even when a piece is sold, traded or broken. Gaps in the sequence are fine; duplicates are not.

The biodiversity data standard used by natural history museums, Darwin Core, defines a catalog number as an identifier (preferably unique) for a resource within a collection, and its own examples show the common styles: plain running numbers such as 145732, a suffixed number such as 145732a, and year-based numbers such as 2008.1334. Each style works for a private collection:

Scheme Example Best for
Running number 0457 Small collections, one buyer, simple spreadsheet
Year plus sequence 2026.031 Collections that grow steadily; the number dates the acquisition
Number plus letter 0457a, 0457b Several pieces bought as one lot, or a specimen that has been split
Prefix plus number TN-0112 (thumbnail), CB-0040 (cabinet) Collections stored by size class in different furniture

Darwin Core also keeps a separate field for other catalog numbers, meant for numbers given to the same object by earlier owners or institutions. Copy those into your record exactly as written. A dealer's stock number, an old collection number inked on the matrix, or a show-lot tag is part of the specimen's history, and recording it is how a later owner connects your piece to a previous catalog.

Where does the number go on the specimen?

On the matrix or the back, never on a crystal face, and small enough that it does not show from the display side. One workable method is a tiny printed paper number fixed with a reversible adhesive, or a small number written on a patch of reversible lacquer on the matrix. Avoid sticky price labels on porous stone: the Canadian Conservation Institute notes that some stone is quite porous and can be stained from the application of price tags or similar labels. For pieces too small or too delicate to mark, such as a micromount or a fibrous zeolite tuft, put the number on the box or mount instead, and never separate the specimen from that box.

What goes on the label, and what goes only in the record?

Think of the label as a summary card and the record as the full file. The label travels with the specimen and has to fit in a box; the record can hold everything.

A good label shows the catalog number, the species (with associated minerals), the locality from most specific to least, and, if you like, your name or collection name. The detailed rules for writing and checking a locality are on the locality labels and provenance guide. The record then adds what does not fit on a card.

Record field Example entry Why it earns its place
Catalog number 2026.031 The link between specimen, label and record
Species and associations Apophyllite with stilbite on heulandite Identifies the piece if the label is lost
Locality as received "Nashik, Maharashtra, India" Exactly as the seller gave it
Size and weight 14 x 12.7 x 5.7 cm, 556 g Distinguishes near-identical pieces
Source Seller name, show, or field trip Provenance chain
Date acquired 2026-10-08 Dates the purchase for insurance and resale
Price paid Amount and currency Insurance, appraisal, tax
Condition notes Two small contacts on the back Proves condition at purchase
Earlier numbers and labels Old label kept, number 1187 inked on base Earlier history
Photo file names 2026-031_front.tif Finds the images
Location in storage Cabinet B, drawer 3 Finds the specimen

Record the locality as you received it in one field, and your own corrected or standardized version in another. Darwin Core handles the same problem with a "verbatim label" field, defined as a verbatim original representation of the written information affixed to the specimen, and its notes say supposed misspellings must not be corrected. That habit protects the evidence: if a dealer wrote "Poona", keep "Poona" in the verbatim field and put "Pune District" in the cleaned one.

Which papers and inks last?

Labels are paper objects and age like any other paper. The Canadian Conservation Institute's guidance on storing works on paper says to use only acid-free materials, and it describes the recommended conservation papers as 100% rag, either buffered at pH 7.5 to pH 8.5 or unbuffered at pH 7. The same note treats stable carbon inks on good-quality paper as light-stable, which is a good reason to prefer carbon-based pigment pens or laser printing over dye-based felt tips.

For inkjet printing, the Library of Congress specifies pigmented inks for digitally printed photographic material it accepts (Library of Congress). Permanence is the reason for that specification, and it is exactly what a specimen label needs.

Two practical rules follow. Keep old dealer and collection labels with their specimen but in a separate paper or polyester sleeve, so an acidic old card does not touch your new label. And never tape or glue a label to anything you might want to remove later.

What should you do with old labels?

Keep every one, with the specimen, and note in the record that it exists. Old labels have their own collectors and their own history. The Mineralogical Record's label archive cites a bournonite specimen with nine labels of previous owners at the Natural History Museum in London, and notes that the Harvard Mineralogical Museum preserved the labels for the first 77,000 specimens in its historic collection.

The same article describes two ways serious label collectors store them. Neal Yedlin arranged labels on 3 x 5 inch filing cards with as much extra information as possible, and the card method holds the labels in stamp collectors' glassine envelopes so the backs, which often show price and date, can still be read. Album mounting is the alternative. Either way, the authors warn that glue and old-fashioned stamp hinges should be avoided. For a private catalog, a simple version works: scan or photograph both sides of each old label, store the image under the specimen's number, and keep the original in a sleeve in the specimen's box. The archive itself now holds over 15,000 examples cataloged, a sign of how much history rides on scraps of paper.

How do you photograph a collection for the catalog?

A photo record does three jobs: it identifies a piece if labels are lost, it documents condition for insurance or a dispute, and it lets you browse the collection without handling fragile specimens.

  1. Shoot the number. Put a small card with the catalog number and a centimeter scale in the first frame of every specimen. File names then follow the number.
  2. Show the front, the back and any damage. Contacts, repairs and chips belong in the record as images, not just words.
  3. Use the same background and light every time. A neutral gray or black card and a fixed light make color comparable across years.
  4. Keep a master file. The Library of Congress lists TIFF first among its preferred formats for digital photographs (Library of Congress), and its format description calls TIFF a tag-based file format for storing and interchanging raster images. Save a TIFF or the camera's raw file as the master, and make JPEG copies for sharing.

How do you keep the catalog itself safe?

Most catalogs die from a single dead laptop. The Canadian Conservation Institute's advice for any digital information is that three copies of the information should be created on at least two different types of storage media, and that one copy should be stored off-site. In practice: the working file on a computer, a copy on an external drive, and a cloud copy or a drive kept somewhere else.

Discs are not a safe long-term answer on their own. CCI rates erasable DVD-RW at only 5 to 10 years of average longevity, and silver-layer DVD-R at 10 to 20 years. Plain formats outlive programs, so export the catalog to a CSV or spreadsheet file each year even if you use a dedicated collection app, and print a paper copy of the core fields. A printout in a drawer survives every software change.

What mistakes break a catalog?

  • Reusing numbers after a specimen leaves the collection.
  • Numbering in pencil on a sticky dot that falls off the first time the piece is dusted.
  • Writing on crystal faces, which lowers value and is hard to undo.
  • Correcting the original label text instead of recording it verbatim and adding a cleaned version.
  • Throwing away receipts. Paperwork is evidence. The Natural History Museum asks donors for permits, receipts, letters, photographs, bills of sale and correspondence, and says its staff may decline a donation if that evidence is not forthcoming. The same papers matter for an appraisal or when selling a collection.
  • Keeping the only copy of the catalog in the same cabinet as the specimens.

Choosing specimens that are easy to catalog well

The easiest piece to catalog is one that arrives with clear dimensions, a weight and a named locality, because those fill half the record before you start. When a listing gives only "India" or nothing at all, record exactly that and resist filling the gap with a guess. Size class matters too: thumbnails want box numbering, cabinet pieces want a number on the base. The specimen sizes guide explains the classes, and the storage and specimen boxes guide covers housing them.

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Frequently asked questions

What is the best way to number mineral specimens?

Use one permanent number per specimen and never reuse it. A running number works for small collections; a year plus sequence, such as 2026.031, dates each acquisition. Add letter suffixes for pieces from one lot. Put the number on the matrix or the back, on the box for tiny or fragile pieces, and in the record.

Should I write directly on a mineral specimen?

Not with a marker on bare stone. Mark the matrix or underside on a small patch of reversible lacquer, or fix a tiny printed paper number with a reversible adhesive. Never mark a crystal face, and never mark fibrous or powdery minerals; number their box or mount instead.

What software should I use for a mineral catalog?

Any tool that exports to a plain format. A spreadsheet with one row per specimen is enough for most private collections. Dedicated collection apps add photos and search, but export a CSV copy each year so the data outlives the program, and keep three copies, one off-site.

What paper should mineral labels be printed on?

Acid-free paper, ideally 100% rag or a buffered conservation paper, printed with pigment inkjet ink or a laser printer, or written with a carbon pigment pen. Skip dye-based felt tips, and avoid adhesive labels that stain porous stone.

What do I do with old labels from previous owners?

Keep them with the specimen in a separate paper or polyester sleeve, photograph both sides, and record any old numbers in your catalog exactly as written. Do not glue or tape them down. Old labels document provenance and can add measurable value when a collection is appraised or sold.

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