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How to Tell if it’s a Crystal or a Rock?

Have you found a cool rock you want to show people but you’re not sure of the terminology? This blog teaches you the difference between crystals, rocks, and minerals, so you can get it right!

Is It A Rock, A Mineral, Or A Crystal?

There are three main classifications we use when we are talking about mineral specimens here at The Stone Circle. If you are coming into hunting for crystals and rocks in the UK for the first time and do not have a geology background, it can be difficult to work out what we are talking about when we call a specific sample either of these names.

This article discusses how you tell the difference between a crystal, a rock, and a mineral. Although all describe types of earth, not all types of earth fit into each category. The categories are as follows…

What is a Rock?

At its most basic form, a rock is a mixture of minerals making up one sample. Rocks can be metamorphic, sedimentary, or igneous. This means they can change over time, be made from layers of sediment, or can form in the magma down in the earth’s crust.

A rock may be made up of one or more minerals. Scottish agates are technically rocks rather than crystals because they are made up from more than one type of material.

a rock made of multiple white and orange minerals held in a pale hand
This rock contains calcite, quartz, possible siderite, and unknown minerals

What is a Mineral?

A mineral is a single type of rock. If a Scottish agate includes chalcedony and quartz, the individual minerals would be different gradients of silica, or silicon dioxide, which is the mineral quartz is made from. A mix of similar minerals can make up a rock. A mix of crystals and minerals can also make up a rock.

To put it how the British Geological Survey team:

“A mineral is a naturally occurring substance with distinctive chemical and physical properties, composition, and atomic structure.”

A black and grey smoky quartz crystal held in a pale hand.
Quartz is made from the mineral silica, or silicon dioxide. It is also crystalline since those silica atoms form regular, repeated patterns.

What is a Crystal?

A crystal is a mineral whose atoms align in regular patterns. If you think of a diamond, each carbon atom has to be perfectly arranged so that it contacts four other atoms. Carbon arranged in any other way might become coal or calcium carbonate – but without that perfect pattern, you don’t have a diamond.

A crystal is a mineral aligned in a specific pattern so that the surface reflects the symmetry of the pattern the atoms make. Crystals have a regular, repeating structure, like garnets. As the UC Berkeley Rausser College of Natural Resources explains:

“Something is crystalline if the atoms or ions that compose it are arranged in a regular way (i.e. a crystal has internal order due to the periodic arrangement of atoms in three dimensions.”

They also added that gems which are not crystalline are described as amorphous.

Frequently Asked Questions: How to Tell the Difference Between Crystals, Rocks, and Minerals?

How to tell if it’s a Crystal or a Rock?

If the mineral specimen contains more than one type of material then this qualifies it as a rock. A crystal is a type of mineral (which might make up part of the rock) whose atoms arrange in set repeating patterns.

We might also call something a rock until we have a firm ID on it, but this would be informally.

What is Rock Crystal?

Just to confuse you in telling the difference between crystals and rocks, we have rock crystal. This is the traditional name for colourless, transparent quartz. Effectively, rock crystal is clear quartz.

Is Every Mineral a Crystal?

Not every mineral has the regular, repeating pattern which would qualify it as a crystal. Minerals must be arranged in a standard pattern by arranging either atoms or clusters of atoms. Some minerals are therefore crystals – but not all.

What is a Rock or Mineral?

A rock is usually a mix of minerals. A mineral is a specific composition of atoms which share physical and chemical properties. Examples of different minerals include silica, calcium, mica, and talc.

Rock, Mineral, or Crystal Conclusion

To round up then:

·       A mineral is a type of rock with a certain composition, atoms, and physical properties.

·       A crystal is a crystalline mineral in which the atoms line up in regular, repeating patterns.

·       A rock is composed of more than one mineral/crystal

Clear as mud. One of our favourite phrases here at TSC.

Until we meet again!




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