How to start a mineral collection
Choose the size format before the species. One 120 by 30 cm shelf holds about 400 thumbnails or 16 cabinet specimens — a 25 to 1 difference in what you can own.
Decide the size format before you decide what to collect. A single 120 by 30 cm shelf holds roughly 400 thumbnail specimens in 3 cm boxes, about 68 miniatures, or about 16 cabinet pieces. That is a 25 to 1 difference in how many minerals you can own, and it settles more than any other early decision.
In short
- Format first, species second. Thumbnail, miniature or cabinet is the decision that determines how many specimens you will own, what they cost to house, and how much of the world's mineralogy you can actually represent. Almost every new collector gets to it second and regrets it.
- There are 6,239 valid mineral species on the September 2026 IMA-CNMNC master list. No collection represents them all and no collection should try. A collection is defined by what it excludes.
- Buy one good specimen rather than ten poor ones. This is the single most repeated piece of advice in the hobby and it is repeated because it is true: the poor ones do not become more interesting, and they are the part of a collection that is unsaleable later.
- Label everything on the day it arrives. Five fields — species, locality, size, source and date — take a minute and cannot be reconstructed later. An unlabelled specimen is a rock.
- The first thing to learn is not identification, it is honest description. Knowing that a specimen has a repaired arm, a bruised termination or a doubtful locality is worth more than knowing its formula.
| Format | Specimen size | Footprint allowed | Approximate number per shelf | What you give up |
|---|---|---|---|---|
| Micromount | Under 1 cm, viewed under a microscope | 25 mm box | About 550 | Nothing is visible without a microscope |
| Thumbnail | Up to about 2.5 cm | 30 mm box | About 400 | Display impact at arm's length |
| Miniature | 3–5 cm | 70 mm tray | About 68 | Roughly six thumbnails per specimen |
| Small cabinet | 5–8 cm | 100 mm footprint | About 36 | Species coverage falls sharply |
| Cabinet | 8–13 cm | 150 mm footprint | About 16 | Everything except the specimens themselves |
The one-shelf arithmetic, with the inputs stated
Here is the calculation, so you can substitute your own shelf. Assume a shelf 120 cm wide and 30 cm deep. A standard thumbnail box is about 30 mm square, so the shelf takes 40 across and 10 deep: 400 thumbnails. A miniature in a 70 mm tray gives 17 across and 4 deep: 68 miniatures. A cabinet specimen needing 150 mm in each direction gives 8 across and 2 deep: 16 cabinet pieces.
That is a ratio of 25 to 1 between the two ends, and it is the real constraint on a collection built in a house rather than a museum. Twenty-five species against one specimen, in the same space, for the same shelf.
Neither answer is correct. A thumbnail collection can represent a whole orefield; a cabinet collection of sixteen pieces can be extraordinary and a thumbnail collection of four hundred can be tedious. What is not defensible is choosing by accident, which is what happens when you buy what appeals and then discover two years later that it will not fit anywhere. The grading conventions behind these size classes are on specimen sizes and grading.
One caveat on micromounts: the count is high but the format follows the species, not the budget. Some minerals simply do not occur large — clinoclase crystals reach 9 mm — and a micromount is the only honest way to own them. That argument is made in full on what is a micromount.
Pick a boundary, and let it be narrow
There are 6,239 valid mineral species on the September 2026 IMA-CNMNC master list, and a further layer of varietal names that the Commission does not regulate at all. A general collection of minerals is not a collection; it is an accumulation.
The boundaries that work are the ones that let you say no. In practice they are:
A locality or an orefield. Cornwall. The Caldbeck Fells. Tsumeb. This is the strongest option for a British collector, because it makes provenance, mine history and old labels part of the subject rather than an administrative chore. Our locality notes are organised this way for that reason.
A chemical class. The copper secondaries, the lead secondaries, the zeolites. It teaches you real mineralogy quickly, because you are forced to separate species that look identical.
A single species across the world. Fluorite, calcite, quartz. Deep, cheap at the entry level, and it makes you a genuine authority on something within a few years.
A size format, collected broadly. A thumbnail collection of one specimen per British locality is a coherent project with an end state.
What does not work is “nice crystals”. It has no edge, so it never becomes a collection, and it is the hardest kind of material to sell on — see where to sell a mineral collection for what that means in practice.
What to buy first, and where the money goes
Your first purchase should be a specimen with a written locality from a seller who will answer questions about it. Not the cheapest piece, not a bulk lot, and not something from a general marketplace with a one-word description. You are buying the answers as much as the mineral.
The value drivers in specimens are locality, crystal quality, condition, size, colour and provenance, roughly in that order and strongly interacting. What that means for a first purchase is that the same money buys either a good small specimen or a poor large one, and the good small one is the one that still looks good in five years. We do not quote prices on this site and there is no catalogue here; what is worth saying is that the relationship between size and cost is far from linear, and the jump from miniature to cabinet is where it steepens most.
Three things to avoid at the start. Tumbled and polished material, which is a different hobby and does not lead into this one. Anything sold on colour alone, because dyed and heat-treated material is common at the low end — the checks are on how to tell if a crystal is dyed. And anything without a locality, at least until you have some judgement — the argument for that is on is a specimen without a locality worth buying.
Where to buy, and the trade-offs between shows, dealers, auctions and online sellers, is covered on where to buy mineral specimens. If you would rather tell someone what you are looking for and be contacted when it appears, that is what our wanted list is for.
The five things to do in the first week
1. Start the catalogue before the second specimen. Five fields: species as written, locality as written, size, where it came from, and the date you acquired it. A notebook is enough. The reasons this cannot be deferred, and the three certainty states that keep it honest, are on labelling and cataloguing a collection.
2. Keep the dealer's label. It is the provenance. An old label attached to a specimen can be worth as much as the specimen, and throwing it away is irreversible — see what ex coll. means on a label.
3. Buy boxes before you buy more specimens. Storage is not an afterthought and the wrong storage causes damage. The conservation guidance on enclosures is summarised on specimen boxes and stands.
4. Do not clean anything. Cleaning is the commonest way a beginner reduces a specimen. Dirt is reversible; a cleaning mistake is not. Read how to clean mineral specimens before you touch a brush.
5. Find out what is in the room. Some species are toxic, a few are radioactive, and some degrade in ordinary light or ordinary humidity. None of that should put anyone off, and all of it is easier to deal with at ten specimens than at a thousand. Start with toxic minerals in a collection and which minerals fade in light.
The rest of the collecting guides cover buying, condition, provenance and storage in more detail as you need them.