#WBW – Rocks, Minerals, Mountains and Hills

Following on from last fortnight’s post, this fortnight is all about geology! This week we’re talking rocks and land formations with one of my fav gal pals! Geology enthusiast, and former science museum volunteer, Rachael!

Rachael is also the talented artist responsible for our beautiful feature image!

Sketches of Igneous Rocks by Rachael Bonebright
Igneous Rock Types Art courtesy of Rachael Bonebright

How is geology relevant to world building?

You don’t really need more than a passing understanding of geology to build a world. Sure, maybe you don’t have some mystical metal or meteorite as a major plot in your story or campaign. But even if you don’t, as Rach puts it;

“Geology is the story of how the earth changes, or how it’s come to be, through its elements.”

Having a basic understanding of the structure of the world and what it’s made of will infinitely help you with all parts of world building. From mapping out your mountain ranges, to deciding on the location of your settlements. A solid understanding of geology helps inform your geography and make for a more realistic, relatable world.

Please keep in mind, neither Rach or myself are geology experts! But we’ll try to break down this complicated science into some of the basics you’ll need for world building purposes. 

So, what’s in a rock?

Basically, there are three types of rocks in the real world. Igneous, Sedimentary and Metamorphic. I asked Rachael to give us simple explanation for each.

Sedimentary rock
“That’s rocks that are made from other rocks and minerals that get compounded by time and pressure.”
Some good examples of rocks in the sedimentary category include limestone and sandstone.

Metamorphic rocks
“A rock that goes through a physical transition under heat and pressure.”
Slate and marble are both metamorphic rocks.

Igneous Rocks
“Those are my favorite, we have a lot of those in the Midwest. Igneous rocks are magmatic rocks. Rocks formed from cooling magma. When magma cools there are gas bubbles that form within the magmatic rock and as it cools the little pockets of gas get stuck, and as it breaks apart and becomes individual pebbles it forms holes. We’d call this a vesicular rock.”
Igneous rocks include basalt, obsidian and granite.


These categories are a great for basic stuff, but sometimes it can get a bit muddled. Some rocks fit into more than one of the three categories, and things can get really heated when physicists and geologists talk about meteorites! With many calling for a separate category to be created just for rocks from outer space! But as Rachael points out;

“Anything that impacts our planet becomes a part of it, and all the things that came to create our planet, and its crust, and core, came from the explosion of a star, light years away. Gold was one of the elements that basically came with it.”

A handy fact to keep in mind when you’re creating your own fictional rocks, crystals and ores for your setting. We’ll talk about ores and gems a little more later, but first let’s talk about where we find these rocks!

What kind of rocks are found in what kind of land formations?

Mountains and hills can be categorized in many ways, and there’s a list of mountain types longer than your arm. We know that these types of terrain are produced through processes of either folding, faulting, igneous intrusion, metamorphism or volcanic activity.

To keep it nice and brief, folding occurs when one or more flat planes of earth are bent or deformed somehow by pressure, stress and temperature, as it sounds the layers of rock literally fold over one another. The Rainbow Basin in California shows us the kind of rock formations that are produced by folding. Faulting is the opposite to folding. Here layers of rock break apart from one another thanks to the stress of the slow movement of the earth over time. The Piqiang Fault in China is a good example of the kind of formation a fault produces.

Intrusive formations such as the Devil’s Tower in Wyoming illustrates the process of igneous intrusion. Intrusive rock formations are created when magma crystallizes underground. As softer rocks closer to the surface wear away, the intrusive formation is revealed.  Metamorphism is the change in the texture of rocks thanks to the transformation that minerals within undergo when they’re exposed to heat and pressure. The Seneca Rocks in West Virginia are a metamorphic rock formation.

Lastly, Volcanic activity are the land formations produced as a result of our tectonic plates converging or diverging and creating ruptures in the earth’s crust, causing volcanoes to form. There are so many different active and dormant volcanic mountains all over the world, like Mount Bromo in Indonesia or Fuji-San in Japan.

So let’s talk a little bit more about our categories of rocks and the kind of areas we’ll encounter them. According to Rach;

“Sedimentary rocks you’ll find in a lot of places, you’ll frequently find them in places that have previously been covered in water. Metamorphic rocks you find literally everywhere. Metamorphic rock is a rock that goes through a changing process, you’ll find that most of the planets been changing since the moment it came into existence. In fact, we’re in a constant state of change it just happens much slower than we can perceive. Igneous rocks we usually find near volcanoes, although we can find these in many places because at one time we were a very hot planet and it took a long time for the planet to cool. Many volcanoes sprouted up, grew dormant, and became mountains as they cooled. Leaving us with rich sources of igneous rocks.”

Back to those ores and gems!

An ore is basically a rock that has significant minerals and elements in it, including metals such as gold, silver or copper, that can be extracted. Gems on the other hand are mineral crystals, which create beautiful ornaments once we cut and polish them.

Usually the value of the mineral or element is weighed up against the cost of extracting it. Ores undergo a process which extracts the element of interest from the waste rock, which may be of any category.

Ore formations are categorized according to a process called ore genesis and certain rocks are known to include deposits of particular ores or gems. For example, kimberlite is an igneous rock which is known to contain diamonds. But how exactly does this happen?

“When you have enough space under the earth’s crust, minerals tend to be drawn to each other. We talked about vesicular rocks before, but amygdaloidal rocks happen when crystals form in the pockets left by gas from a magma flow.” That’s the basics, according to Rach. With diamonds specifically, “It takes a very long time, millions of years. What you will find sometimes is with larger spaces, more time, and more pressure you’ll get harder crystals that form. Diamond is composed of carbon that has found a pocket of gas in an area under the earth’s crust, and slowly over time just drawn more and more carbon towards that pocket until it was a crystal, then that crystal was condensed under severe pressure and eventually, it became the diamond.”

This process behind the formation of diamonds is quite similar across the board when it comes to ore formations and precious stones. It’s all about heat, time and pressure! So, now we have a basic idea of the science behind our world, let’s talk about getting creative!

Using Fantasy or Science Fiction Elements

If you’re wanting to use unique elements of your own creation in your world, then Rach and I have a tip to help you out!

Firstly, whether it’s fantasy or sci-fi, it’s important to be reasonable! Rachael and I decided to look at some popular fictional examples to explain what we mean.


Elli: Let’s talk about meteorites again! Let’s talk about Kryptonite.

Rach: Kryptonite is just a piece of Krypton, an old planet. But it’s reasonable there would be chunks of that planet still floating around in space. It’s also radioactive… and there is a big myth that meteorites that come down from space have picked up space radiation. It does help perpetuate the myth of being the mystical rock that solved or caused all our problems and all that Mcguffin… But in the case of superman, kryptonite is a necessary Mcguffin, he is otherwise a benevolent god.

Elli: In the case of the narrative structure of Superman and the DC universe, this works fine, this is his one weakness and as a rule, it’s pretty harmless to us. But you’re right. As writers, we don’t want to be perpetuating myths that are harmful to progress in reality. So being clear and reasonable about the effects of whatever space rocks we’re creating is really important.


Elli: As a huge D&D nerd, I love Mithril. It’s obviously the best metal for armour in the game.

Rach: Mithril, I think it’s supposed to be a very beautiful, elegant metal. We associate it with silver which is actually very soft. I think it’s one of those creations that kind cherry picks the best of what we already know and puts them together. So, it’s strong as steel, but beautiful and elegant and workable as silver. Which we associate with our contemporary idea of elves in fiction and fantasy. We make hybrid and mixed metals all the time, most common jewelry is only a certain percentage of gold and then you get pyrite and other metals so it’s sturdier than it is.”

Elli: Mithril is definitely something of a hybrid between silver and steel. Tolkien kept it reasonable by making it very rare, only the Elves had it. Which is something that falls out the window when you enter the realms of tabletop gaming and you’re playing in high magic, high fantasy settings. I think when you’re dealing with situations like this, looking at the cost of these hybrid metals in the real world is a good way to keep things reasonable. Mithril should be more expensive than gold, to your players, for example.


Elli: Adamantium, it gets used a lot in science fiction and fantasy.

Rach: If you’re going to give it a mystical or very substantial or narrative property, make sure you make up the rock or metal as well. So, you have Adamantium for wolverine in the X-Men…

Elli: Based on the mythical Adamantine metal from Greek Mythology.

Rach: But then Admantine Spar is a mineral that actually exists! And it’s not that strong! That’s the sort of nitpicking inconsistency that can get brought up in those extended nerdy conversations we fans like to have.

After talking about the creations of other world builders, I thought I’d put Rach on the spot and ask her what sort of fantasy or science fiction rock she would create.

“I suppose… I’d want to make a crystal that would grow in a shape it usually wouldn’t. Like, I love sailor moon’s crystal. I’d create something like a fiber-optic selenite that naturally grew in the shape of roses.”

Whatever you do, let the science behind geology and geography help inform your creative decisions about the world!

Don’t forget to check out more of Rachael’s awesome art work here, or follow her on Instagram!

All photographs in this post were used under the creative commons agreement, and found on Wikimedia or Flickr.
Check out the awesome photographers by clicking on the following links (in order of their appearance) to take you to the full size image and the artists Flickr gallery.

Mike Lewinski
Hefin Owen 
Ajay Tao
Kevin Walsh
Charles de Mille-Isles
Stephen Nakatani
Jim Accordino
Jim Brickett
C Amalia
Hans Johnson