Mineral or rock? The basic difference between stones

A mineral is a naturally formed solid with a definite chemical composition and an ordered internal structure (a crystal structure); quartz and calcite are minerals. A rock is a natural mixture of one or more minerals; granite is a rock made of quartz, feldspar and mica. Put simply, minerals are the bricks and rocks are the walls built from them.

What is a mineral?

The body that defines minerals and approves new ones is the International Mineralogical Association (IMA). Under the definition it published in 1995, a mineral is “an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes.” This boils down to four conditions:

Condition	What it means	Example
Natural	Formed in nature, not made by people	A ruby crystal grown in a laboratory is not a mineral; it is called “synthetic”
Solid	Occurs as a solid in nature	Ice is a mineral; liquid water is not
Crystal structure	Atoms arranged in an ordered, repeating lattice	The six-sided crystals of quartz reflect this order
Definite composition	Can be written as a chemical formula	Quartz is SiO₂, calcite is CaCO₃

There are a few historical exceptions: native mercury, for example, is liquid at room temperature yet still counts as a mineral.

The IMA’s official list, updated in September 2026, contains 6,239 valid mineral species, and the number grows every year. Some were first described in Türkiye; konyaite, named after Konya, and trabzonite, named after Trabzon, are examples. Yet most of Earth’s crust is made of just a few mineral families: silicate minerals make up about 90% of the crust, led by the feldspars and quartz.

What is a rock?

A rock is a solid mass formed when minerals (and sometimes volcanic glass or organic matter) come together naturally. Some rocks consist almost entirely of a single mineral: marble is mostly calcite, quartzite is quartz and rock salt is halite. Most rocks, though, contain several minerals; granite and basalt are examples.

Rocks are grouped by how they formed into three families: igneous, sedimentary and metamorphic. How these families turn into one another is explained in The rock cycle.

	Mineral	Rock
What is it?	A single natural substance	A mixture of minerals
Chemical formula	Yes (quartz: SiO₂)	No; composition varies from place to place
Hardness and density	Definite, within a narrow range	Depend on the minerals it contains
What decides its name?	Composition and crystal structure	Its minerals, texture and origin
Examples	Quartz, calcite, pyrite	Granite, marble, sandstone

The easiest practical clue: look at a broken surface with a magnifier. If you see grains of different colours and lustres, you are most likely looking at a rock.

Gemstones that are rocks

“Gemstone” makes most people think of minerals, but some famous ornamental stones are actually rocks. Lapis lazuli is a blue metamorphic rock made mainly of lazurite, calcite and pyrite; its golden specks are pyrite. Jade is not a single mineral either but a shared name for two different rocks, nephrite and jadeite.

One mineral, several names

A mineral’s name and the name of the stone in a piece of jewellery are not always the same. Types of a mineral distinguished by colour or appearance are called varieties:

• Amethyst (purple), citrine (yellow), rose quartz and smoky quartz are all quartz.
• Ruby and sapphire are varieties of the same mineral, corundum.
• Emerald and aquamarine are varieties of beryl.

Mineraloids: no crystals

Some natural substances look and behave like minerals but have no ordered crystal structure. These are called mineraloids.

• Opal: made of silica containing water. The play of colour in precious opal comes not from crystals but from tiny silica spheres stacked in an orderly way.
• Obsidian: a natural glass formed when lava freezes before it has time to crystallise.
• Tektite: glass formed from Earth rock melted and thrown out by large meteorite impacts; despite frequent confusion, it is not a meteorite.

Organic gems: made by living things

Some stones are products of living organisms. Because they are used in jewellery they are called “organic gems”, and CIBJO, the World Jewellery Confederation, counts organic materials used in jewellery as gemstones.

• Amber: forms when the resin of ancient trees fossilises over millions of years. Having no crystal structure, it is also described as a mineraloid.
• Pearl: built from layers of nacre produced by oysters and mussels.
• Coral: the calcium carbonate skeletons of marine animals.
• Oltu stone: a type of jet from the Oltu district of Erzurum, formed from coalified wood.

The carbonate crystals in pearl and coral are made entirely by a living creature, so under the IMA definition they are not minerals; the same substances can count as minerals once geological processes have been involved. Coal, by contrast, is a sedimentary rock formed from plant remains.

From space: meteorites

Meteorites are space rocks that fall to Earth and survive the trip through the atmosphere. London’s Natural History Museum divides them into three main groups:

• Stony meteorites: made mostly of silicate minerals. Most meteorites found belong to this group; the most common kind are chondrites.
• Iron meteorites: almost entirely iron-nickel metal; they are thought to come from the cores of asteroids that melted early in their history.
• Stony-iron meteorites: contain roughly equal amounts of metal and silicate. In pallasites, olive-green olivine crystals are embedded in metal.

Under the IMA definition, substances formed on other bodies in space also count as minerals. So a meteorite is a rock, not a mineral, but it contains minerals. If you wonder whether a stone you found might be a meteorite, see Is my stone valuable?.

How stones are labelled on this site

Every stone page starts with a label showing which group the stone belongs to:

Label	Meaning	Examples
Mineral	A single mineral species that fits the IMA definition	Calcite, pyrite
Variety	A type of a mineral distinguished by colour or appearance	Amethyst, ruby
Rock	A natural mixture of minerals	Granite, marble
Mineraloid	A natural, mineral-like substance without a crystal structure	Opal, obsidian
Organic gem	A material made by living things and used in jewellery	Pearl, amber
Meteorite	Rock or metal that fell from space	Chondrite, pallasite

You can see how these groups fit together with the mineral classes on the classification page.

Why the distinction matters

The first question to ask when identifying a stone is “mineral or rock?”. Minerals show definite properties such as hardness, streak and cleavage, so simple tests can identify them. With rocks you need to look at the individual grains and the texture. How to do these tests is explained in How to identify a stone.