Our visiting geologist turned writer, Chris Large, is with us again. This time he is looking at:
Rocks and Ore Deposits. Oh My!
Try writing a woodland scene where the only word you‘re allowed to use to describe the wondrously varied flora is ‘trees’. No oak, no cedar, no maple, not even any pencil pine or scrubby undergrowth – just trees.
Writing convention encourages the discrimination of vegetation, even though not everyone can be expected to know what a cedar, or maple tree looks like. But when it comes to rocks, ‘thou shalt use the word rock, and rock shall be the word, for rock is the word that shall describe the rock’.
As a writer, you’re telling the story through the point of view of a character. If you use a scientific term (or a pseudo-scientific term), it’s going to jar unless there is a reason for the character to know it. (Think of the medieval Alchemist looking for the Philosopher’s Stone). But just because your character has never heard of metamorphic rock, that doesn’t mean these kind of rocks don’t exist in your world.
Imagine your characters are scrambling up a cliff. I know I’m a weirdo geologist, but I tend to look at (and think about) rocks, and I’m sure you do too on some level.
‘Mangalore pulled himself over the cliff’s razor sharp rim. The dark, brittle rock had a heavy grain, like wood, and splinters of it needled his forearms opening painful, bloody cuts across his palms making the climb a slippery and treacherous ordeal.’
Now, rather than a rocky cliff, we have an metamorphic rock with veinlets of a mysterious mineral which appears to cut like glass. I guess what I’m trying to say is that, in the same way you strive to paint a colourful picture of your world’s flora and fauna, you can also sketch in the rocks and geomorphology, even though you can’t use the correct scientific word you can describe the rock and if it is a rock that your character is familiar with. He/she will have a name for it.
The average medieval peasant would have had words for flints, poor soil like clay, good red soil or black soil for ploughing, and they might use peat for burning. He/she might have seen marble on a fancy church floor or in a church sculpture. Depending on where they lived and how prosperous the local village/town was, they would be familiar with sandstone, flint, limestone and hard chalk which were used in the construction of churches or castles. A stone mason might have a preference for working in one stone over another, just as a carpenter would use different woods for different jobs.
If you’re writing fantasy and volcanoes are erupting all over the map, raining pyroclasic ejecta down upon your story from on high, you need to research what kind of effect this has. Your character might not know words like rhyolite (light-coloured volcanic rock), basalt (dark volcanic rock), tuff (ashfall deposit), pumice (light, glassy rock), or obsidian (volcanic glass). He/she might not know that molten rock below the ground-surface should be referred to as magma or that once it’s extruded, it can be called lava. But your character will be familiar with all these things and would have their own descriptive names for them.
Basalt is the most commonly used name for volcanic rock in literature. It’s dark, often black, and sometimes has small holes through it called vesicles. These are little bubbles of gas that were trapped in the lava as it quenched. Your peasant might describe pumice as the floating-stone and attribute magical properties to it. Caves, in the form of lava tubes, also occur in basalt. But you don’t have to use accepted nomenclature. If you’re writing fantasy rather than science fiction, you could substitute your own rock names like, “mountain glass” for obsidian.
Knowing how a rock forms and where it comes from could help you write a passage like:
‘Catching a bright flash in the shallows, Mangalore stooped and plunged his hand into the clear, icy water. After fumbling about among the river-washed pebbles, he pulled out a dark, angular shard, roughly the size of and ear of maize.
“Elka!” he barked triumphantly, holding the shard aloft. “Mountain glass! It must have washed down from the Peaks of Fire and Ash.”
Elka grinned wearily. “Now we will have arrowheads,” she said, relief evident in her voice. “And if we’re lucky, a buck for our supper.”
Sedimentary rocks are composed of weathered fragments of other rock types. They’re often formed under water, rivers and streams being extremely efficient mechanisms for transporting large amounts of sediment over long periods of time. And like the rings on an old tree, sedimentary rocks contain a historical record of what has happened in your world in the past.
You might be wondering why this would ever come up in your story, but consider this: such rocks may contain fossils of ancient plants, beasts or even extinct civilisations. If volcanoes erupted nearby (or far away) the rocks may contain layers of ash, or even tuffaceous beds. If a meteor struck your world in the distant past, throwing a cloud of glassy dust into the atmosphere, you could well find evidence of it in sedimentary rocks. And let’s not forget that slabs of sandstone make great building material. What an irony it would be if your thriving, law-abiding city was built from sandstone containing the fossilised relics of an ancient empire of creatures possessed of dark magics and evil urges? What if the dead were to rise right out of the walls of the towering sandstone mansions of the city’s most venerated leaders?
Caves often appear in fantasy books and there are often convenient glowing worms or rocks so that the characters can light their way. Knowing how a cave is formed and what kind of formations the characters are likely to come up against, makes your description of the cave’s tunnels much richer.
Cave systems can occur in limestones when weak acids within groundwater act to dissolve the rock over time. Changes in the chemistry of the groundwater can determine whether it is dissolving or precipitating carbonate. Limestone is also a sedimentary rock and can form in two ways, firstly via the breakdown of a coral reef, or secondly as a chemical precipitate from a supersaturated groundwater. This is how stalagmites and stalactites form.
Caves can also occur in sandstones in coastal areas where wave action erodes the porous sandstone around faults in the rock. A coastal sandstone cave would not normally be deep or form an extensive network. Often coastal caves form blowholes.
One of the best-known metamorphic rocks is the common schist, and frankly, you don’t need to know any more than that. I mean let’s face it, one totally screwed up piece of crud looks pretty-much like another totally screwed up piece of crud. They have a ‘grain’ and tend to split along the grain of the rock. They’re often veined and appear stretched. Marble is a metamorphic rock, having been converted from limestone. Where would king’s palace be without marble? Which brings us to…
Unless the inhabitants of your world are going to base their technology on stone and wood alone, they are, at some point, going to have to get their hands dirty in a mine. And while your inner tree-hugger might prefer to believe that elves and other faerie-kind sit around reading love poems all day under majestic, riverside willows – those pewter goblets, ornate belt buckles and exquisitely sharp swords were all forged from metal, which is dug from the ground.
Middle Earth had a few mines, the Mithril mines of Moria being the most prominent. Saruman the White also set his goblins to work for want of iron. Where the hobbits, elves and men came upon their iron, copper, lead and various other metals we can only speculate. Of course a mine is not something that need necessarily appear on a world map, but a large mine would attract significant numbers of workers. In the real world, towns of thirty thousand or more people spring up in mining districts, so it’s a little odd that there aren’t more mining towns in fantasy realms. The only race that seems to get into mining are dwarfs.
If you’re going to describe a mine, you should try to get a few of the details right because – and this is only an empirical observation – a lot geologists read sf/f. The first thing to know, because I’ve come across this in books before, is that although they can be paired to make stunning jewellery, gold and diamonds are unlikely to naturally occur together. Diamonds will generally occur on their own within an intrusive rock known as Kimberlite, or can be washed into river systems. Gold is usually found in veins (often with quartz).
Iron can be won from magnetite ores. Magnetite is (you guessed it) magnetic, and therefore not too difficult to locate when it’s close to surface. When discussing polymetallic deposits, copper and nickel often occur together.
There are so many styles of mineralisation, it would be impossible to go into them all, suffice to say that if you are planning to insert a mine into your world, you will benefit from doing a little research first. The internet is a great resource for information on ore-forming minerals.
To cut this very long story short, not everyone needs to be Kim Stanley Robinson, but if you want your maps and rock
descriptions to make sense, do a little research. For some writers, this post will be so much nonsense because their world rides around on the back of a turtle, or exists in a bubble in fluid space. Or better yet, is nothing more than a gleam in the eye of the mighty Dream King.
But for those who want something Earth-like and quantifiable, this may help. Geology isn’t rocket science, it’s rock science, which, with a little application, anyone can master to a basic level of understanding (look at me). If you want a river that looks like the Mississippi, find the Mississippi on a map. Observe its luxurious curves, how it flirts with the landscape.
To make your map sexy, first make it real. Only then can you go about moulding it into the total package, making it the papery equivalent of a certain spacefaring minx from the 1960s. On the other hand, if you rush it without paying your respects to natural processes, you’re more likely to end up with the original piecemeal clunkmeister.
That’s it from Chris. I’d like to thank him for taking the time to put these posts together. If you’d like to catch up with him, he can found here.
Chris is a mineral explorer and has spent more than 15 years looking at rocks, sawing them in half, drilling holes into them, licking them, and sticking little eyes on them and giving them to his kids. Many of those 15 years have been spent in a tent in a desert. He now writes from home in Hobart while completing a MSc in Economic Geology.