Crystal vs mineral: what is the difference
A mineral is a natural, ordered solid of definite composition; a crystal is one grain with its own faces. Quartz is a mineral; a quartz prism is a crystal.
A mineral is a naturally occurring solid with a definite but variable composition and an ordered atomic arrangement; a crystal is one grain of it grown with its own faces. Nearly every mineral is crystalline, but not every specimen shows crystals: all 176 Handbook sheets in this site's reference set name a crystal system, and 5 describe none.
In short
- Mineral is a kind of substance; crystal is a kind of object. A mineral is defined by composition and atomic arrangement. A crystal is a single piece of ordered material bounded by its own faces. Quartz is a mineral; a quartz point is a crystal of it; a quartz vein is often massive quartz with no crystals showing.
- The textbook definition. Tropper’s EOLSS chapter defines a mineral as a naturally occurring homogeneous solid with a definite, but not fixed, chemical composition and a highly ordered atomic arrangement, and says the ordered arrangement indicates that a mineral is in a crystalline state.
- Survey of 176 Handbook sheets: every one is crystalline, five show no crystals. All 176 Crystal Data fields open with a crystal system. 171 describe crystals or named crystal forms such as cubes, octahedra, prisms or plates. Five describe only aggregates, masses or powder: berthierine, cornwallite, faustite, mendipite and pararealgar.
- Most species come both ways. 109 of the 176 Crystal Data fields use the word massive, and 100 of those also describe crystals. A massive specimen is the same mineral as a crystal of it.
- Many label words are not mineral names. None of amethyst, rock crystal, selenite, obsidian or moonstone is a row on the September 2026 IMA list, and nor are the group names apatite and tourmaline. Quartz, the mineral behind amethyst and rock crystal, is.
| What the Crystal Data field shows | Sheets (of 176) | Examples | What it means for a specimen |
|---|---|---|---|
| Opens with a crystal system | 176 | Monoclinic 54, orthorhombic 44, hexagonal 29, cubic 22, tetragonal 15, triclinic 12 | The mineral is crystalline, whatever the specimen looks like |
| Describes crystals or a named crystal form | 171 | Fluorite: cubes and octahedra to 2 m; grossular: dodecahedra to 15 cm | Crystals of it exist, though not every specimen has them |
| Uses the word massive | 109 | Fluorite, grossular, turquoise | Massive material of the same mineral is common |
| Crystals and massive both | 100 | Grossular: dodecahedra to 15 cm, also granular and massive | Massive and crystallised pieces carry the same name |
| Aggregates, masses or powder only | 5 | Faustite: fine-grained massive; pararealgar: fine powder; mendipite: columnar or fibrous aggregates | Crystalline but no free crystals described |
| Uses microcrystalline or cryptocrystalline | 8 | Chrysocolla, turquoise, quartz, goethite | Crystals too small to see; still a crystalline mineral |
| Calls the mineral amorphous | 0 | One sheet uses the word, for amorphous silica as an associate of hydrobasaluminite | No species in the set is described as non-crystalline |
What is the difference between a crystal and a mineral?
A mineral is a substance with a definition. In Tropper’s EOLSS chapter, Introduction to the Mineralogical Sciences, a mineral is a naturally occurring homogeneous solid with a definite, but not fixed, chemical composition and a highly ordered atomic arrangement. Definite but not fixed allows solid solution and zoning. The same chapter says that synthetic compounds not known in nature cannot be called minerals or have mineral names in a strict sense.
A crystal is an object made of crystalline material: a single grain whose ordered atomic arrangement shows on the outside as flat faces. The chapter defines crystalline materials as three-dimensional periodic arrays which show a precise geometric arrangement of their atoms. The Handbook uses the word the same way. Its Crystal Data field gives the system first, then the habit: as prismatic crystals, to 1 mm for one species, or fine-grained massive for another.
A species is a further step. The rule the IMA applies, as quoted by Hawthorne in Mineralogical Magazine 87 (2023): a mineral is a distinct species if the set of dominant constituents (ions or neutral species) at the sites in the crystal structure is distinct from that of any other mineral with the same structural arrangement. Hawthorne notes that this rule for species is distinct from the formal definition of a mineral. The September 2026 IMA list counts 6239 currently valid species.
Is every mineral a crystal? What 176 Handbook sheets show
Method. We took the 176 Handbook sheets in this site’s reference set as pdftotext text and extracted each Crystal Data field, from the label to Physical Properties. Then we ran case-insensitive regex searches. Crystal forms means the word crystal or crystals, or a named form: cube, octahedron, dodecahedron, trapezohedron, pyritohedron, rhombohedron, scalenohedron, prism, pyramid, plate, platelet, tabular, acicular or bladed. The twinning sentence was excluded so that a twin law does not count as a habit.
Results. All 176 open with a crystal system, and none calls the species amorphous. The only sheet with the word is hydrobasaluminite, which names amorphous silica among its associates. 171 describe crystals or named forms. 109 use massive, and 100 of those also describe crystals. Eight describe microcrystalline or cryptocrystalline material, among them chrysocolla and turquoise.
The five with no crystals described are berthierine (microcrystalline oolitic aggregates), cornwallite (microcrystalline or radial fibrous crusts), faustite (fine-grained massive), mendipite (columnar or fibrous aggregates and cleavable masses) and pararealgar (fine powder). Each still has a crystal system on its sheet. These are crystalline minerals that the sheets do not describe as free crystals. Aggregate habits have their own vocabulary, for example botryoidal.
Is quartz a crystal or a mineral? Names on labels the IMA list does not carry
Quartz is a mineral: the September 2026 IMA list has a row for it, SiO2. A single quartz point is a crystal of that mineral, and a quartz crystal label can mean exactly that. The words go wrong in the other direction. Many names on labels are not mineral species, and a search of the list’s name column finds no row for any of these:
- Variety names: amethyst and rock crystal (quartz), selenite (gypsum), moonstone (feldspar). See why is my amethyst losing colour and is labradorite a moonstone.
- Group names: apatite (three calcium species), tourmaline (42 species by formula), microlite and axinite.
- Rock and glass names: obsidian has no row. Man-made glass sold as crystal is not naturally occurring, which Tropper’s definition requires.
The list does include a few rows that test the solid, crystalline definition: Mercury (Hg), Ice (H2O) and Opal (SiO2·nH2O), all grandfathered. Mercury is a liquid at room temperature. They are historical exceptions on the list, not the pattern. Name endings across the list are counted on why do mineral names end in -ite.
Crystal words on labels, and what to check
Read a label in two parts: the mineral name, then the habit. Fluorite, cubic crystals on matrix is a species and a description; fluorite, massive is the same species. The first part should be an IMA name, a group name marked as such, or a variety name with its species. The second part says whether you have crystals. The fluorite sheet covers both: cubes and octahedra to 2 m, and nodular, botryoidal, granular and massive material.
Crystal-form terms have precise meanings. A double terminated crystal has natural faces at both ends; a twin is two individuals related by a law (mineral twinning explained); a pseudomorph has one mineral’s shape filled by another. A polished point or sphere is a worked object, with no natural faces. Checks for cut, dyed or glass pieces are on how to tell if a crystal is fake.
Identification works on the mineral, not the crystal. Hardness, streak, cleavage and density are properties of the species and work on massive pieces too; how to identify a mineral specimen sets out the order. More terminology is in the collecting guides. Nothing on this site is offered for sale; the wanted list is the only commercial route.