Is a mineral a crystal or is a crystal a mineral? Rocks, crystals and minerals. What is the difference?
Before explaining the differences between minerals, crystals, and rocks, you need to know the difference between an element and a compound.
What is an element?
A group of atoms of the same type form an element. Elements are listed on the periodic table, and you’ve heard of some of them: gold, silver, copper, sulfur, oxygen, and carbon. The chemical formula of an element is simply the element. The most common elements in the earth’s crust are: O for Oxygen (about 47%), Si for Silicon (about 28%), Al for Aluminum (about 8%), Fe for Iron (about 5%), Ca for calcium, Na for sodium, K for potassium, and Mg for magnesium.
What is a compound?
Compounds, on the other hand, are made up of molecules that contain different types of elements. For example, table salt contains sodium (Na) and chlorine (Cl). Sodium chloride is a molecule, and a group of sodium chloride molecules together form a compound. The chemical formula for sodium chloride is NaCl. (Note that there are two different items listed in that formula.)
Now that you know what elements are compounds, you can understand the definition of a mineral.
What are minerals?
Minerals are made of compounds. Table salt is a mineral with a formula of NaCl. Epsom salts are a mineral with a chemical formula of MgSO4. Minerals have a definite and fixed chemical formula.
Minerals are solid. Liquids are not minerals, so while water is not a mineral, snowflakes are.
The minerals are obtained by inorganic processes. Minerals are made by natural processes, such as the cooling of magma below the ground, precipitation, and condensation. Minerals are not manufactured inside living organisms. So feldspar is a mineral, but a kidney stone, even if it has a consistent chemical formula, is not a mineral.
Minerals are made up of molecules in a repeating pattern, called a lattice. Mineral molecules stick together in repeating patterns. Common patterns are cubic, tetragonal, hexagonal, monoclinic, orthorhombic, trigonal, and triclinic.
Crystals are a special type of mineral.
Crystals are a special type of mineral. They are a subset of minerals. So while all crystals (not made by biological processes) are minerals, not all minerals are crystals. Crystals are minerals that have flat faces that meet at regular angles. It takes a lot of geologic time and space to “grow” for large, beautiful crystals to form.
rocks
Rocks are composed of one or more different minerals. For example, granite is a rock. It does not have a uniform structure. It is a slurry, usually made of feldspar, quarts, and mica. You can usually look at a piece of granite and see black mica, pink feldspar, and white quartz.
That old Venn diagram
So if you imagine a Venn diagram (circles within circles), the smaller circle is crystals, since crystals are a special case of minerals. The circle of crystals is completely enclosed in the circle of Minerals, and the circle of Minerals is completely enclosed in the circle of Rocks.