Before learning how minerals are formed, it is important to know what minerals are, since minerals are different from rocks.
What are minerals? Minerals are naturally occurring solids. They are made of a consistent chemical compound and they have a repeating pattern. They are made from by non-organic processes.
So, salts are minerals. Salts are made from inorganic matter (and in fact, they don’t contain any carbon). Salts have a consistent chemical composition. Table salt is the familiar NaCl. Epsom salt is magnesium sulfate, or MgSO4. The molecules bond together in a repeating pattern. NaCl forms in a cube shape, and magnesium sulfate has a monoclinic structure, which has angles other than 90 degrees and unequal lengths.
While salts are minerals, kidney stones are not, since kidney stones are formed by biological processes. Coal is also not a mineral, since coal was formed from decaying plant matter.
How are minerals formed? So, if biological processes are out, how are minerals formed? There are three different ways minerals form. Also, most people think in terms of minerals “growing” instead of forming. Minerals start out small and more molecules of the same chemical compound join the first group, increasing the size of the mineral. The minerals attach together like pieces of a puzzle. Perhaps a better analogy than puzzle pieces, however, would be a honey comb. In a honeycomb the hexagons fit well together. Once a mineral molecule lines up with another mineral molecule, they are stable.
1. Slow cooling from a molten mass: The magma under the crust of the earth slowly cools. Minerals grow during that slow cooling process.
2. Precipitation from a liquid: A saturated or super saturated liquid cools and evaporates. The chemicals dissolved in the solution precipitate out, and you’re left with minerals.
3. Condensation: While water isn’t a mineral because it is a liquid, snowflakes formed by condensation in clouds are indeed minerals.
What are crystals? Crystals are a subset of minerals. While all crystals are minerals, not all minerals are crystals. Crystals form the exact same way minerals do, but crystals are solid minerals that have flat surfaces that meet at regular atoms. Different crystal shapes come about because of the different sizes of the atoms that make up the chemical compound the mineral is composed of.
For crystals to form instead of just minerals, a long stretch of geologic time is required. Crystals require a long time to form, while minerals don’t require as long. Additionally, sufficient space is required. Crystals need room to grow their flat surfaces. If the crystal keeps running into another solid, it can’t grow. Crystals might form in molten magma in a gas-filled cavity.
Gwen Nicodemus has two children that she’s been homeschooling all their lives. Gwen also teaches science and math classes in a local homeschooling cooperative. As a temporarily retired engineer, Gwen keeps her brain active by writing unit studies and little books for her kids whenever someone gets interested in a new topic. Check out the great free resources, including unit studies, videos, tutorials, and little books at http://UnitStudiesByGwen.com©2010, Gwen Nicodemus
