Rocks do not grow like organisms - they do not feed or increase in size from within, but crystals really do grow: they add successive layers of atoms from a solution, usually over thousands or even millions of years. Meanwhile, the stones that "grow" in fields every year have not grown at all - frost pushes them toward the surface.
This question is only childish at first glance. The answer depends on what we are talking about: a rock, a crystal, or a boulder that emerges from the ground in the middle of a field every spring. Each of these "stones" behaves differently - and each has its own story.
Crystals really do grow - layer by layer
A crystal does not eat or breathe, yet it grows. When dissolved silica circulates in a hot underground solution, its particles settle on a nucleus and arrange themselves into a perfectly ordered lattice - atom by atom, layer by layer. This is how crystallization works: a crystal keeps growing as long as it has material to build with and room to expand.
We explain how a geode differs from a druse and a crystal cluster in connection with the Warsaw mineral fair in the article mineral fair in Warsaw: geode, druse, or crystal cluster.
The most beautiful evidence is provided by druses and geodes. These are cavities in rock where quartz or amethyst crystals grew from circulating hydrothermal solutions over thousands, and sometimes millions, of years. That is why a split geode is lined inside with a cluster of glittering points - each one literally grew inside a stone chamber.
How do stones form?
Rock has a different biography. It is born when magma solidifies into granite or basalt, when sand and silt compact on the seafloor into sandstone and limestone, or when older rocks transform deep inside the Earth under immense pressure and temperature. From that moment on, the stone no longer grows - water, ice, and wind can only break it down and wear it smooth, so over time it generally becomes smaller.
Amber followed a separate path: it is tree resin that hardened and remained buried in sediments for millions of years. We explain in detail how amber forms in a separate article.
Where do new stones in fields come from every year?
Farmers could swear that stones grow in fields: every spring they gather a fresh "harvest" from ground that looked clean in autumn. The culprit is frost heaving. The ground repeatedly freezes and thaws, and these small seasonal movements push boulders toward the surface year after year - the stone has not grown by a millimeter; it has simply ridden upward like an elevator.
The boulders themselves did not come from nowhere, either. Most fieldstones in Poland are glacial erratics that the ice sheet dragged from Scandinavia and abandoned when it melted thousands of years ago. The field does not "give birth" to them - it merely gives them back.
How fast does a stone grow?
In nature, crystallization is usually measured in thousands and millions of years. Even cave stalactites, considered relatively fast-growing, typically increase by fractions of a millimeter to a few millimeters per year, depending on the amount of water and dissolved carbonate. Travertine or cave pearls grow "before your eyes" - that is, for entire centuries by geological standards.
By contrast, salt or alum can crystallize in a household jar within a few days or weeks. The mechanism is the same, but the rate is incomparable. This is the simplest way to see with your own eyes how a stone grows.
From the Brazi workshop
The crystal clusters and druses in our workshop are literally stones that grew - nature shaped them over thousands of years, and we only added the setting. In our collection, you will find both raw clusters and jewelry featuring this mineral - 10% off with the code BRAZIBLOG10.
So when someone asks whether stones grow, the answer is: rocks do not, but crystals do - only at a rate that makes a human life seem like a blink. And if you would like to get to know the most famous of these "grown" minerals more closely, take a look at our guide to what rock crystal is.
Since crystals grow in cavities within rocks, it is no wonder that for years people took them to be the work of something more than nature - we write separately about the most famous such mistake, namely crystal skulls.