GEOLOGY 101:

What Are Crystals & How Do They Form? ☁

In hopes of bridging the gap between science & spirituality, we have created a simple Geology 101 guide to help you better understand the geological properties of crystals & the science behind it all. This series aims to provide a basic understanding of crystals on a practical level, as well as the ways in which they can be identified. Whether you are a crystal newbie or a long-time collector, becoming familiar with crystals in this way can prove helpful when buying & ultimately growing your collection. Along with being a deeply interesting topic, it also sets the basis for understanding crystals on an energetic level.

Rocks, Minerals, Crystals & Gems, What's The Difference?

While many people use the terms rock, mineral, crystal, & gemstone interchangeably, it is important to note that these terms actually have specific meanings.

What is a Rock?

In geology, a rock is simply a collection of other things. Officially, it is a naturally-occurring collection of one or more types of minerals (or mineraloids), held together in a solid mass. There are three main types of rocks, classified by how they were formed: igneous (formed by solidification of cooled magma), sedimentary (formed by the accumulation of sediments), & metamorphic (once igneous or sedimentary rocks, that have metamorphosed as a result of intense heat &/or pressure.) Each of these rocks are formed by physical changes (melting, cooling, eroding, compacting, or deforming) that are part of a process known as the rock cycle. An example of an intrusive igneous rock is granite, comprised mainly of the minerals quartz & feldspar.

So if minerals make up rocks, what exactly is a mineral?

To meet the definition of "mineral" used by most geologists, a substance must meet five requirements:


✦ is naturally occurring - means that people did not make it e.g. steel is not a mineral.

✦ is inorganic - means that the substance is not made by an organism e.g. wood & pearls are made by organisms & therefore not minerals.
✦ is usually a solid - means that it is not a liquid or a gas at standard temperature & pressure e.g. water is not a mineral because it is a liquid. (but ice is!)
✦ has a definite chemical composition - means, in the simplest terms, every time we see the same mineral it has the same chemical composition that can be expressed by a chemical formula e.g. halite will always have a chemical composition of NaCl.
✦ has an ordered internal structure - means that the atoms in a mineral are arranged in a systematic & repeating pattern, which is why minerals often take on a defined crystalline structure e.g. glass in not a mineral as it does not have a crystal structure.

There are several thousand known mineral species, & new ones are discovered every year. A class of substances, which don’t exactly meet the criteria to be a mineral, are sometimes known as "mineraloids." Two well-known examples are Mercury & Opal, which both lack a crystal structure.

What is a Crystal?

While the term crystal may bring forth images of dazzling Calcite clusters & sparking Amethyst geodes, the word can also simply refer to ice crystals stashed inside a snowflake or the salt crystals found inside your kitchen cabinet. So what does a grain of salt & an Amethyst geode share in common? In simple terms, both of these crystals have a highly ordered microscopic crystal structure. The atoms & ions are arranged in a repeating pattern or lattice that can be defined as one of the seven crystal systems – hexagonal, cubic, trigonal, triclinic, orthorhombic, monoclinic, or tetragonal. The atoms in glass, for example, are in a random & disorganised arrangement, which is why glass is neither a mineral nor a crystal. Since all minerals have a defined crystal structure, in a sense all minerals are crystals. However, not all crystals are minerals either because they are organic (like sugar) or because they are formed through artificial or synthetic processes.

What is a Gem?

Gemstones are beautiful minerals, rocks (like lapis lazuli), or organic matter (like amber) that have been cut & polished for use in jewellery or other adornments. These gems are usually highly prized, rare & durable, as well as possess physical properties that hold aesthetic value. Gemstones are typically divided into two groups: precious (like diamond, emerald or ruby) & semi-precious (amethyst, garnet or turquoise). In some cases, lab-created or synthetic, chemically identical versions of natural stones are made & called gems.

The Formation of Crystals

To understand the formation of crystals, we must start at the very beginning. All matter is made up of substances called elements that emerged during the early stages of our Universe. As the very first generation of stars died, spectacularly exploding & scattering their ashes across the cosmos, tiny mineral crystals emerged. It is believed microscopic crystals of diamond & graphite, both pure forms of the abundant element carbon, were the first minerals to exist, followed by only a dozen or so others. 4.6 billion years later, our solar system was formed &, in turn, hundreds of new mineral species were born.

Planet Earth was now beginning to take form. From a whirling cloud of dust it transformed into a white-hot molten ball of magma. Overtime, the outer layer of our planet cooled into a crust. Yet still bubbling & boiling inside the Earth’s mantle, far below where we stand today, this mineral-rich, molten magma continues to exist. Magma plays an important role in the formation of certain minerals, though it is far from the only ingredient needed for crystal creation

Natural crystals are formed in many ways, though the overall process is generally the same - molecules gather (in a process known as nucleation) to stabilise, as a hot substance slowly cools & hardens, creating a solid. Many crystals start small but, as more atoms join in to create a uniform & repetitive pattern, the crystal grows. This process is called crystallisation & can happen many different ways, such as when water evaporates from a natural mixture or, as mentioned before, when magma/molten rock hardens.

Some crystals like Peridot & Diamond crystallise at high-temperatures within the mantle. Others like Topaz & Ruby crystallise in magmas or gas bubbles in volcanic rocks. Pegmatite magma rich in beryllium or boron can produce crystals such as Aquamarine or Tourmaline. Near the Earth’s surface, solutions can cool or evaporate causing minerals to precipitate. In this process, if the mineral solution forms from silica-rich rocks such as sandstone, silica-rich minerals like Amethyst, Agate & even Opal will form. Under ideal growing conditions - based on a wide range of factors such as time, temperature & pressure - minerals may grow into the well-formed geometric crystal shapes we value so highly as crystal collectors.

Forming over hundreds, thousands or even millions of years, it is no wonder why crystals have dazzled cultures across the globe, gracefully balancing the line between science & magic. Within they carry the DNA of the Earth, holding the memories, secrets & stories of a distant Universe. They are forged through chaos, dancing between fiery forces & deep waters, & yet they emerge. Whether you value crystals for their history, their beauty or their spiritual benefits, we can all agree that these gifts from Mother Nature are truly something special.

Next Step: Mineral Properties & IdentificationBack To Learn