What is the difference between rocks, minerals, and gemstones?

Have you ever wondered what secrets could be hiding inside a simple rock? Or have you ever admired the sparkles of a diamond wondering, “What makes up this stunning jewelry?"

This post is all about rocks, minerals, and gemstones. We will uncover the differences between rocks, minerals, and gemstones, discover how they are all formed, and explore some super cool examples from each category.

Differences between rocks, minerals, and gemstones

We can start to understand the differences between rocks, minerals and gemstones, by having a look at their definitions.

What is a rock?

A rock is a solid, natural material composed of one or more minerals.

What is a mineral?

A mineral is also a solid, naturally occurring material that is composed of one or more chemical elements. It has a defined chemical composition and crystalline structure.

What is a gemstone?

A gemstone is generally a mineral that is cut and polished professionally for use in jewelry.

Rocks

A rock is a solid, natural material composed of one or more minerals. Depending on where and how the rocks were formed, as well as their mineral composition, we can classify rocks into three main categories:

igneous rocks
sedimentary rocks
metamorphic rocks.

Igneous rocks

Igneous rocks are formed either from solidified magma or lava. Some examples of igneous rocks include: granite, basalt, rhyolite, and scoria.

Sedimentary rocks

Sedimentary rocks are formed through the deposition of sediments, which are then compacted and eroded over time. Some examples of sedimentary rocks include: sandstone, shale, limestone, and dolomite.

Here’s a fun fact about sedimentary rocks.

Some sedimentary rocks are made almost entirely from the compression of the calcium carbonate (CaCO3) present in the shells of dead sea creatures, giving birth to limestone. Others are made from the compacting and weathering over millions of years of the material originating from dead plants, giving birth to coal.

Metamorphic rocks

The metamorphic rocks are either igneous rocks or sedimentary rocks, which were transformed over long periods of time because of high pressure and high temperature conditions in their environment. Varying the temperature and pressure conditions a material is exposed to, can change its structure, creating a new form.

Some examples of metamorphic rocks include: marble, mariposite, novaculite, and soapstone.

Minerals

A mineral is also a solid, naturally occurring material that is composed of one or more chemical elements. It has a defined chemical composition and crystalline structure. Minerals can form through crystallization from magma or precipitation from solution.

Crystallization from magma

When minerals form through crystallization from magma, the chemical elements are brought together by their environmental conditions. Thus, the varying temperature and pressure conditions, as well and the chemical composition of the magma they reside in, shape the minerals in their crystal form.

Precipitation from solution

This type of mineral formation happens when there are too many particles in a solution, meaning the solution is supersaturated, and those particles come together to form a solid. That is what happens with the salt in the Dead Sea in Israel. The water there is supersaturated with salt and thus the salt minerals started precipitating into a growing salt layer.

My favorite case of mineral formation from precipitation is in the Naica cave of crystals in Mexico.

The Naica cave contained a supersaturated solution of ions of calcium and sulphate, which combined with the water molecules to form selenite crystals. Being a closed environment, without anyone or anything disturbing the process for hundreds of thousands of years, this place was perfect for the growth of the giant selenite crystals that now inhabit the Naica Cave.

Minerals and their crystal structure

Each mineral has a unique crystal structure given by which chemical elements are present and how they are organized in the 3-dimensional space of the crystal. The 3D organization is very important because some minerals might have the same chemical composition, but they are very different minerals due to the organization of the crystal’s 3D lattice.

For example, both aragonite and calcite minerals have calcium carbonate (CaCO3) as the main ingredient, but their crystal structure is very different, leading to two different minerals with different physical properties.

Isn’t it fascinating how similar, yet so different, minerals with the same composition can be?

Other examples of minerals are: pyrite, olivine, talc, and fluorite.

Gemstones

A gemstone is generally a mineral that is cut and polished professionally for use in jewelry. However, there are some exceptions. One exception is amber, which is not a mineral. Amber is a fossilized resin from ancient trees that solidified slowly over time due to the various high temperature and pressure conditions it was exposed to.

Not all minerals form gemstones. Gemstones are coming from those minerals that possess certain qualities. The qualities of a gemstone are:

beauty, which refers to their color and clarity
rarity, which tells us how uncommon they are
durability, which is their resistance to scratching and breaking

All these qualities are leading to their high value in the jewelry industry. Gemstones can be precious and semi-precious gemstones.

Precious gemstones

There are only four precious gemstones: ruby, sapphire, emerald, and of course, diamond. Did you know that diamonds can have many different colors? To learn what these colors are, check out this other blog post on the colors of diamonds.

Semi-precious gemstones

There are more semi-precious gemstones than precious ones. Some examples of semi-precious gemstones include: amethyst, lapis lazuli, onyx, and moonstone.

There are many other beautiful gemstones, other than the ones I mentioned. Let me know in the comments section what is your favorite gemstone and I might highlight it in a future blog post and video. My favorite gemstone is opal, and I’ll definitely be creating a blog post/ video about opals in the future.